[question] actions for batton

Hello,

I have a question.
How to detect on your own page (IO) pressing Next, Cancel, Back?
I would like to assign some actions for them.
I have this function:

Function sprawdzanie
!insertmacro INSTALLOPTIONS_DISPLAY "some.ini"
!insertmacro INSTALLOPTIONS_READ $R9 "some.ini" "Field 1" "State"
WriteRegStr HKLM "Software\Tclanydy\sygypy" "SerialNumber" $R9

System::Call '$TEMP\eInsuect\test.dll::test() i() .r3'
${If} $3 == '0'
MessageBox MB_OK "The serial number is invalid"
GoTo Again
${ElseIf} $3 == '1'
Abort
${EndIf}

FunctionEnd

The function works correctly. But
When I press Cancel again to verify the key, as is the press on the Back. To go further I need to provide a valid key; /

Better take a look at the included example testnotify.nsi and even better upgrade to nsDialogs.