Setting a default VM to open

Hi, I have a number of VM's (Win7, 8 and a Win7 Boot Camp) and am finding that when I open an .exe file in OSX Finder it always wants to open the Boot Camp VM. I would prefer it to start up another VM but can't see a way of setting a default VM to always open Windows files in Finder or some other method of achieving this. Any ideas?

Thanks, Julian