Running under User Access Control

Hello,
For historical reasons, we've always required that our customers install and run our application with UAC turned off, but we're now seeking to change that.
The problem is, we have customised scripts running NGen and RegAsm commands that will need to be granted elevated privileges at install time.
Is there a flag we can set in InstallShield to enable this?

Also, as we distribute both setup.exe and .msi formats, is there any flag we need to specify to msiexec?

Thanks