This can be done using the Microsoft Visual Basic for Applications Extensibility 5.3 (VBIDE) library. There's some great examples at CPearson.com. I typically use this to insert snippets of code while I'm developing. I would personally be uncomfortable executing code stored in an excel sheet, but I tested this and it does work.
My worksheet:
A
1 MsgBox "I'm a test."
2 MsgBox "So am I."
I set up an empty subroutine that we will then insert into from the excel sheet.
Private Sub ProcToModify()
End Sub
And the subroutine that will actually insert the code into ProcToModify
:
Sub ModifyProcedure()
Dim VBProj As VBIDE.VBProject
Dim VBComp As VBIDE.VBComponent
Dim CodeMod As VBIDE.CodeModule
Dim StartLine As Long
Dim NumLines As Long
Dim ProcName As String
Set VBProj = ActiveWorkbook.VBProject
Set VBComp = VBProj.VBComponents("Module1") ' specify module to modify
Set CodeMod = VBComp.CodeModule
Dim ws As Worksheet
Dim rng As Range
Dim cell As Range
Set ws = ThisWorkbook.ActiveSheet 'change this accordingly
Set rng = ws.Range("A1:A2") 'and this
For Each cell In rng
ProcName = "ProcToModify"
With CodeMod
StartLine = .ProcStartLine(ProcName, vbext_pk_Proc)
NumLines = .ProcCountLines(ProcName, vbext_pk_Proc)
.InsertLines StartLine + NumLines - 2, cell.Value 'insert each line at the end of the procedure to get them in the correct order.
End With
Next cell
End Sub
Called at runtime like this:
Public Sub main()
ModifyProcedure
ProcToModify
End Sub
One Big Gotchya:
Before running this code, you need to go to Excel>>File>>Options>>Trust Center>>Trust Center Settings>>Macro Settings and check the "Trust access to the VBA project object model".
I would imagine that's because allowing access to the project object is a fairly concerning security risk.
From the cpearson.com site I linked to earlier:
CAUTION: Many VBA-based computer viruses propagate themselves by
creating and/or modifying VBA code. Therefore, many virus scanners may
automatically and without warning or confirmation delete modules that
reference the VBProject object, causing a permanent and irretrievable
loss of code. Consult the documentation for your anti-virus software
for details.