function isPosInteger(inputVal){
var oneChar;
inputStr = inputVal.toString();
for(var i=0; i < inputStr.length; i++)
  {
   oneChar = inputStr.charAt(i)	
   if(oneChar < "0" || oneChar > "9'")
       return false;  
   } 

return true;
}

function validateEnrollment(enroll)
{
if((enroll.length != 21) || ((enroll.substring(5,6) != "S") && (enroll.substring(5,6) != "F") )  || (parseFloat(enroll.substring(14,17))<1) || (parseFloat(enroll.substring(7,9))<1)  ||  (! isPosInteger(enroll.substring(14,17))) ||  (! isPosInteger(enroll.substring(7,9))) )
 return false;
else
 return true;

}