Changing MUI_INSTFILESPAGE_FINISHHEADER_SUBTEXT based on events during installation.

Hi,
I have a question. How can I change the
!define MUI_INSTFILESPAGE_FINISHHEADER_SUBTEXT from "Patch successfully applied." to "Patch UNsuccessfully applied." if there are errors during installtion?
Same question for
!define MUI_FINISHPAGE_TEXT
Is it possible to do this? Because I really need it.

Use a variable in the value and set the variable to text you wish to display.