search for: add_visit_for_this_pt_9

I am trying to implement a check all and uncheck all button for my check boxes. Here is what I have below. I am getting this error each time: Error: document.myform.add_visit_for_this_Pt has no properties Source File: http://localhost:3000/AddPatientVisit/addvisits Line: 1 Strange that I can''t seem to pass value into the function. Thanks for your help! <SCRIPT