How can I verify the completion of an .msi installation?

Hi experts.

I am developing an html application that will be used to install a number of different programs.  On a page will be a list of programs that will need to be installed.  I have already used a jscript that checks for specific registry entries, determining if any of the programs have already been installed.  If a program has been installed, a check mark image is made visible next to the name of the program.

If a program has not been installed, the user will see an install button.  Clicking on that will then run the normal installer (usually an .msi).  After the installer completes successfully, I would like to put a check mark next to the name of the program.  How can I verify within the hta file that the external installer has completed?  Is there a script I can run that will wait for a process to complete? I would like to stick with jscript, but any solution that accomplishes this will do.

Thanks!!!