I want to be able to use my macro for lots of different projects, so the
filenames that I use throughout the macro need to be easy to change.

So I've set them up at the beginning of the Macro so they're easy to
identify using the following sequence:

myPath = "U:\PM&E\09 Project Work\253 Kazakhstan Project\02 Project
Services\03 Man Hour Reports\"

mySourceFileBase = ActiveWorkbook.Worksheets("Imported
Data").Range("F5").Value

mySourceFile = myPath & mySourceFileBase

So I can put the file name that I want to import data from in the workbook
containing the macro and hopefully not have to open the VBE to alter the file
references.

and it's used it correctly in this line:

Workbooks.Open Filename:=mySourceFile

but after I've activated a different window, I can't get the syntax right
for activating the other window that mySourceFile refers to. It wants the
file name reference ("RF Man Hours Report 0506.xls").

Is there any way that I can use mySourceFile as a window object?