Locking the mouse inside the window

I'm running two copies of diablo 3 on two seperate monitors and the mouse has the freedom to move between the two of them. This causes all sorts of problems so I'd like to find a way to lock the mouse inside the main screen. I'm at a loss so I thought I'd try to forums. Any ideas?

Did you turn off broadcast all on the other chars screen. And did both account have the same video setting too. You have to set the D3 video setting in game and also the fps setting of both account must be the same. Hope this help.

The video settings are identical and the broadcasting is turned off on the 2nd screen but the mouse still is able to move outside the main window. Very frustrating!

[lax]

The setting you want is in your Character Set (select it in the top left pane and this setting is in the General tab), labelled:
"Lock cursor inside game window while focused" and it is a drop-down box set to "if the game requests it" by default. Set it to "yes" to lock the cursor in the game window.

I selected that option but it only seems to work some of the time. Usually just after I switch windows it gets unlocked and won't get locked again until I switch back and forth. I don't see any pattern. I know I'm doing something wrong I just can't figure out what.