Hi headkaze, Thanks for the advice, it worked - sort of. I'm sure it's because I'm being a muppet. I'm testing this using a keyboard, so I'm pressing the Escape key like I do with every other emulator. After I press Escape, the WHDLoad game quits back to AmigaDOS, so the {MULTIPLY} is definitely being sent to WinUAE, but a split second later WinUAE quits without resuming my Amiga batch file. I've put 'echo' commands in there to prove it's stepping through the batch file, but it doesn't get to show them, so GameEx must be terminating WinUAE. I'm wondering if it's worth me continuing with this, since I found this link after making my original post, and didn't realise the trouble you went through to create the WinUAELoader. Plus, I didn't realise what the GameBase project was all about! Hmmm...