As far as I know, there is no way to put a middle mouse click in a mapkey. If you find a way, I'd love to know. Some times the enter key on the keyboard is the same as the middle mouse, but that's not 100% of the time.
Anand, I think a things may be a little confused here. Am I right that you want a mapkey for Done, Done/Return, Done, Done, etc. so you don't have to keep pressing the MMB? If so, open up a suitable cascade of menus and record a mapkey for Done, Done/Return by picking each from the open menus. Now if you hit the assigned keyboard key repeatedly you will get one or the other or both in sequence until you are "Done". (In the "old days" before recordable mapkeys, users would sometimes write a mapkey with a long string of Done's and Done/Return's trying to cover all possibilities.) David
check this: http://www.microsoft.com/france/accessibilite/training/windowsvista/mousekeys.aspx it's in french but you should find the same in english; in winXP you can use the mouse with the keyboard; I read if you press the "VerrNum" key 5 seconds, you access to the mouse control with keyboard. Good luck