How to debug installation

[Hazard]

Hi, everyone.

I have a very simple project. I created 3 InstallScript function, one of them, InitializeINSTALLDIR

#include "ifx.h"
#include "iswi.h"

// The keyword export identifies MyFunction() as an entry-point function.
// The argument it accepts must be a handle to the Installer database.
export prototype InitializeINSTALLDIR(HWND);

function InitializeINSTALLDIR(hMSI)
    STRING szInstDir;

    NUMBER nvCount;
    INT result;
begin
	nvCount = MAX_PATH;
	
	result = GetEnvVar ("FIPLAN_HOME", szInstDir);
	
	result = MsiSetProperty(hMSI, "INSTALLDIR", szInstDir);
	
	INSTALLDIR = szInstDir;
end;

This function is connected with button "Next" on the Dialog "WelcomeInstall".

But, when I click "Next" my installation stopped. Please, check attachment. How I can know the reason for stopped installation?

[#2]

F5 start debugging.

Firstly, you need to define a custom action to call your InitializeINSTALLDIR function.

Then specify DoAction event's argument with your CA's name, set the condition to 1