You should use code tags when posting vba/sql .
If you highlight the text involved, then click on the # button above the posting area, that text will be tagged automatically in your post.
Please clarify in English before telling more about the code.
What is cboPurchaseNumber? Where do its values come form?
What is [PurchaseNumber]?
Why did you create, but did not Dim strOffice?
You could try this (guessing, since there are several things containing "PurchaseNumber" in their names )
Code:
strFilter = "[PurchaseNumber] " & strOffice