When a user clicks anywhere in a document protected for forms (other than in an active formfield) the focus moves to a page with formfields that are active.
Assuming you are using legacy form fields, you can designate a macro to run on exit from a formfield.
You can put the following in an AutoOpen and AutoNew macro in your form template:
Code:
Sub AutoOpen()
' Set macro button response to one click rather than double-click
' Macro written by Charles Kenyon based on help from Bill Coan on newsgroup
'
Options.ButtonFieldClicks = 1
'
End Sub
This makes a single click activate the macrobutton.
Making Forms with Microsoft Word