What’s worse than getting a runtime error in Excel VBA? A compile error. That’s because the actual error is not always highlighted, rather the opening Sub or Function statement. “Sub or Function not Defined” indicates a compile error. VBA displays this message when it cannot find what is referenced by name. This article gives several examples of this compile error and how to correct them.

VBA is compiled (translated) into machine language before it is executed. Compile errors halt the compile process before procedures are executed.

Best practice:  Frequently check for compile errors from VB Editor. From the Debug menu, choose Compile VBAProject. No news is good news when nothing seems to happen.

Issue 1: Typos

Typos are the most common cause of “Sub or Function not Defined.” If Excel highlights (in yellow or gray) the keyword or procedure it can’t find, you have a great head start on your game of Hide and Seek.

Best practice:  Follow Microsoft’s naming convention and always include at least one capital letter whenever you create a name (exception: counter variables like n). Always type the name in lower case. When you leave the statement, and the name stays in all lower case, you have found a typo.

Contrary to its message, “Sub or Function not Defined” is not limited to procedures. The statement below causes this message. Can you find the typo?

          Worksheet("Summary").Select

Worksheets is the required keyword. The “Summary” worksheet object is a member of the Worksheets collection. The Worksheets collection contains all the worksheet objects of a workbook. Excel VBA has several collections.

Tip: All VBA collections end with “s”:  Workbooks, Sheets, Cells, Charts, etc.

Issue 2: Worksheet Functions

VB Editor may be the backstage to the worksheets in front, but not all worksheet props have been brought backstage. These “props” are functions that don’t exist in VBA. Worksheet functions like CountA cause “Sub or Function not Defined”:

          intCount = CountA("A:A")

The WorksheetFunction object is the “stage hand” that lets you call worksheet functions from VBA, like this:

          intCount = WorksheetFunction.CountA("A:A")

Issue 3: Missing Procedure

Less frequently, the called procedure is truly missing. After you check for typos, and you’re sure you coded the called procedure, perhaps you are missing a library. Tools, References is the next place to look.

From VB Editor Tools menu, choose References. The References dialog box opens. If VBA has identified a missing library, the last library with a checkmark will start with MISSING, followed by its name. Most of the time, you can simply scroll down the alphabetical list of libraries and check the missing library, then choose OK.

Fortunately, a missing library happens infrequently, usually related to a recent change. Perhaps you upgraded to a newer version of Excel. You purchased a new computer. You received a workbook from someone with an older version of Excel. Or you created your first macro that calls Solver Add-In.

The Solver project is not added to VBA when you enable the Solver Add-In, as shown below. At Solver project is near the top of the list of references, so you don’t have to scroll down to find it.

Your own macro workbooks can behave like Solver. Every Excel workbook has a built-in VBAProject. See MyFunctions in the screenshot above? MyFunctions is simply VBAProject renamed in a macro workbook. The workbook is open, so the Subs in MyFunctions run from the Developer tab. Even so, “Sub or Function not Defined” occurs when MyFunctions is not checked, and a procedure is called from a different macro. Simply check its project as an available reference.

Best practice:  Assign your VBA projects a meaningful name. From Project Explorer, right click the macro workbook. Choose VBAProperties, then type a Project Name with no spaces.

Issue 4: Unavailable Procedures

“Sub or Function not Defined” also occurs when the procedure is not available to the calling procedure in the same workbook. This error is related to Public vs. Private procedures. By default, Sub and Functions in standard modules of the Modules folder (seen in Project Explorer) are public. Standard procedures can be called by any procedure in the project. You can make a procedure private by adding the Private keyword, like this:

          Private Sub Initialize()

Tip:  All the macros shown in the Macros dialog box of the Developer tab are Public. The list excludes public functions.

Subs and Functions in worksheet modules are private. They can only be called from the worksheet (like clicking a button) or another procedure in that module. The same is true for user forms.

You can remedy “Sub or Function not Defined” by deleting the Private keyword from a procedure in a standard module. Sorry, you cannot remedy calling a procedure in a worksheet module from another module. Think of standard modules like public parks, and worksheet modules like private property. No trespassing allowed!

Issue 5: Declaring a Routine That Doesn’t Exist in the Specified DLL

The sub you’re trying to use could be a part of a DLL that needs to be referenced. So not declaring a DLL or declaring the wrong one will cause the compiler to not find the sub or function that you are trying to use.

A DLL is a dynamically linked library of a body of code that is compiled and is meant to provide some functionality or data to an executable application (like the VBA project we’re working with). A dynamic library is loaded by the VBA project when it needs it. DLLs are used in order to save developers time by utilizing built and tested bodies of code.

You will need to do some research to determine the library that your sub or function belongs to, then declare it in your code using the Declare keyword in its simplest form:

Declare Sub sub_name Lib “library_name”

To read more about accessing DLL functions and subs from VBA, check out: https://docs.microsoft.com/en-us/office/client-developer/excel/how-to-access-dlls-in-excel

Issue 6: Forgetting to Write It

Finally, it’s possible that it just hasn’t been written yet!

If you realize that the sub that has been highlighted for you by the VBA compiler doesn’t exist, then the solution is to create it. To know whether it exists or not, just search for it on the project level using the Find tool in the VBA IDE.

Selecting the ‘Current Project’ scope will allow you to search for the sub in the entire workbook. You can also do that for the other workbooks where the sub might reside.

Wrap Up

“Sub or Function not Defined” is a compile error that occurs when VBA cannot find a procedure or other reference by name. A typo is the most common cause of this message.

See also: Compile Error: Expected End of Statement and Compile Error: User-defined Type Not Defined

Additional assistance from Mahmoud Mostafa