Running an EXE file from SETUP.LST

I need to run a program that installs a 3rd party software (in addition to my application) when the user installs my program.
Is there any way to execute a program from SETUP.LST file or is it necessary to modify the setup1.exe file?
(I'm using VB 5.0)
Thank you

Moved.

Modifying setup1.exe is an option and I've done it but I believe that Inno will allow you to do what you want much more easily.