You could potentially minimise the document before showing the userform but it may be easier to code the form so that any actions other than clicking the one button you want results in the document closing or being locked. You haven't given us enough information to give you an exact answer.

What is the code that displays the userform?
What is the code that runs when the user clicks the Cancel button?
Is the code in the document itself or an attached template?

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Andrew Lockton
Chrysalis Design, Melbourne Australia