I got bored yesterday and decided that I wanted to play bgee in borderless windowed mode.
So I spent a few hours yesterday and today and whipped up an ahk solution.
Its a scripting language for windows, though I'm not sure it'll work on windows 8.
I tried to make it support multiple monitors, but I can't test it myself.
There's a readme but here's the tl;dr version:
Download the zipped up exe file (In 7zip format).
Extract and place bgeeBW.exe in the main directory of BG:EE.
Run bgeeBW.exe, don't be alarmed if it makes a shortcut for Baldur.exe.
Press alt+b to switch from borderless windowed mode to regular windowed mode
Press alt+q to quit bgeeBW and revert the game to regular windowed mode
Pressing alt+b when BG:EE is not running but bgeeBW is running will launch the game.
You can download the zipped up exe and readme here or from this link (which includes the script):https://www.dropbox.com/sh/s575yegm9a81ou5/xgdp1HfZYu