Is it possible to set a variable by starting the setup with a commandline?

Example

My setup has a %_MVG_UPDATE%. This variable gets set by checking the registry bla bla bla.

If it's TRUE, I'll hide some wizard dialogs. This way the users doesn't have to go to all dialogs again.

But sometime when I run it I like to see the dialogs. So I like to set a variable %_MVG_OVERRULE% = TRUE by starting the setup.exe /admin

Is this possible?

Tnx

Michel