Your post made me realise I could do something along those lines using a batch file, with contents like this:
Code:
"C:Program Files (x86)ATI TechnologiesATI.ACECore-StaticCLI.exe" Start Load profilename="eyefinity"
G:gamessteamsteam.exe -applaunch 550
"C:Program Files (x86)ATI TechnologiesATI.ACECore-StaticCLI.exe" Start Load profilename="normal"
However, the call to steam.exe starts up the game in a different process/thread so that it returns to the batch file immediately, then changes video mode back to normal before the game has even fired up.
I had a quick look at the AutoIT page, but it just seems like another scripting language and I didn't see anything that would make it better than a plain old batch file in this regard.
I guess that, now I've figured out how to change video modes in a batch file, the issue is now Steam-related, not widescreen-gaming related, so I'll take the question elsewhere. Thanks for the input.