Vista - Call sub in Excel ThisWorkbook module from VBS

I'm trying to execute a sub residing in an Excel workbook,
in the "ThisWorkbook" module, but the VBS file fails to
see the function "ConvertFormNumber". The following
is an example of my current code:

Set oXL = CreateObject("Excel.Application")
Set oBK = oXL.Workbooks.Add(argFullName)
oXL.Visible = True
oBK.Application.Run "ConvertFormNumber"

Can someone please correct my code above or
otherwise show an example of how to execute/call
a subroutine residing in the "ThisWorkbook" module
from a VBS file?

Thanks much in advance.