How to run external program from installer (no DOS window)

I have installer and I need run external program in installation. I extract my util via:

File myutil.exe

Next I want to run this program with some parameters. I use function ExecWait:

ExecWait "myutil.exe /some /parameters" $0

My problem is that if I use this function, DOS windows is opened. All works fine but this isn't much user friendly. Is there any option how to run external file with no DOS window?

Thanks for your help