Passing command line variables through

Can i do something like that:

I want to call
blasetup.exe param1 param2 etc.
after finishing the setup it should start bla.exe with the parameters.
bla.exe param1 param2 etc.

How can I do this?

Juse use Exec or ExecWait if you want to wait for it to finish.
You have two possible places to call this from, .onInstSuccess or in the last section (make sure that section is always picked [RO or hidden] if you want it to always get executed.)