Closing workbooks

Hello,

I have two workbooks, one of which has a userform with a cancel button on.
When one workbook is opened the other automatically opens and the Userform pops up.

When I click the cancel button I want both workbooks to close, but they don't, only one of them closes. The code I have used is:

Workbooks("Unit13.xls").Close False
Workbooks("Unit13 (Replenishments).xls").Close False

Yet if I assign this code to a command button in one of the worksheets it closes both??

Any ideas why this is happening?

Thanks

Alex