Update progress bar for a child setup.exe

Hi,

My requirement is to run a setup.exe (which extracts a Basic MSI created using Installshield) in UI sequence. I had also written a custom action to launch the exe in UI sequence. But that was not updating the progress bar. So after referring links like http://community.flexerasoftware.com...?t-194662.html I was able to update the progress bar successfully. As mentioned in the link I have 2 functions, one to add total ticks/reset the progress bar and another to increment the ticks. So, in brief my installscript looks something like this.

function AddTotalTicks(hMSI)
begin
//code to add total ticks and reset it
.....
.....
.....
end;

function ProgressBar(hMSI)
begin
//code to increment the ticks
....
....
....
end;

function Installsetup(hMSI)
begin
....
....
LaunchApplication(szApplication,szCmdLine,"",SW_NORMAL,INFINITE,LAAW_OPTION_NOWAIT);
ProgressBar(hMSI);
end;

I have exported function AddTotalTicks() and have called it before SetupProgress standard action in UI sequence.
This works for me. The setup.exe launches and the progress bar is displayed correctly.
Now, this is fine if the setup.exe is installing for the first time. Say, setup.exe is already installed and I run my installer again, windows installer will detect it and skip its installation. But, the progress bar will still be seen incrementing as if the installation is in progress. I want to stop the progress bar from incrementing because it is already installed and want to continue if the setup.exe is a upgrade.

How can I achieve this.

Thanks,
vj