InfoPath Dev

Folks, We have Department list which is coming form SP. I had bind them with one Multi Select Check Box list. As one of the value of Department is "All". Now I have to do validation that If User Selects "All" then he/she should not allow to select any other value. We are using MOSS 2007 & Infopath Desktop Application.

Unfortunately, the behaviour you are describing will not be easy to accomplish using just the MSLB control.  What you can do it create another checkbox that display beside the control that says "All".  If this checkbox is selected, create a rule that disables or hides the MSLB control so that you cannot select any of the values.  You can then just do a check on the data source to see if All was selected and then ignore all of the MSLB values.