Triggering page from inside section

I have code that has a section. In this section, I have a statement
ExecWait "mixcheck.exe" $1
${If} $1 == 1
Abort
${ElseIf} $1 == 2
blah
${EndIf}

mixcheck.exe is extracted as part of the section code after some other stuff has been done.

What I want is that if the "blah" code runs, it will display a custom page after its run the section code but if the "blah" code does not run, it wont display this page.

How do I do this?

Set a variable, and in the post-install page's prefunction call abort if the variable isn't set.