Hi Greg - it can be done.

In your Excel VBProject, you need to create a reference to the 'Microsoft PowerPoint 8.0 Object Library' or whatevery version you have available.

Your procedure would then look something like this:

Sub RunPowerpointMacro()

Dim oApp As PowerPoint.Application

'create an instance of Powerpoint and make it visible
Set oApp = New PowerPoint.Application
oApp.Visible = True

'open the presentation
oApp.Presentations.Open "C:\MyPresentation.ppt"

'run the macro
oApp.Run "MyPresentation.ppt!Module1.TestMacro"

End Sub