MUI enable and disable callback function for cancel button

[ChocJunkie]

Hi,

I want my installer to go to the finish page if the user clicks 'cancel' on any page. Therefore I'm using

code:
!define MUI_CUSTOMFUNCTION_ABORT _onUserAbort



Function _onUserAbort

   [...]  // calling function for going to finish page

   Abort

FunctionEnd

I need to call 'Abort' because otherwise the installer will quit while executing my function called the line above.

I know, 'MUI_CUSTOMFUNCTION_ABORT' sets the function called when hitting the cancle/X button. When I've reached my finish page, I want to disable the functionality and call another function when clicking cancel/X.
Can I do this using MUI_CUSTOMFUNCTION_ABORT or do I have to use NSD_OnClick on every page?

Thanks!

CJ