A simple Javascript code

I have a page with a dropdown and two textboxes. The javascript code checks to make sure that if the dropdown says? **Appointment Made** or**? Patient Scheduled,** the appropriate text boxes will have dates in them. When the page loads and the drop down shows either of the two above, all works fine but when I change the drop down the script does not work. I have put an alert statament after the third line and do see that when I make a change to patient_status, the variable a gets updated but for some reason the script fails and does not prompt. For example if the page loads and Appointment Made is selected, the script will prompt, but if I change the drop down to Patient Scheduled, it will not prompt. Thank You. <SCRIPT LANGUAGE="JavaScript"> function calculate() { a= [login to view URL]("EditRecordpatient_status").value; b= [login to view URL]("EditRecordSurgery_Date").value; c= [login to view URL]("EditRecordConsult_Date").value; alert(a); alert(b); alert(c); if (a=="Appointment Made" && c=="") { alert('You have scheduled a patient for consultation but the consult date is missing!'); return false; } else if (a=="Patient Scheduled" && b=="") { alert('You have scheduled a patient for surgery but the surgery date is missing!'); return false; } else { return true; } } [login to view URL]("Mod0EditRecord").onclick=calculate; </SCRIPT>