function isAlphaNumberKey(e,evt) {
              
          var charCode;          
          if(e && e.which)
             { //if which property of event object is supported (NN4)
                e = e
                charCode = e.which //character code is contained in NN4's which property
             }
            else
                {
                    e = event
                    charCode = e.keyCode //character code is contained in IE's keyCode property
                }              
                //alert(charCode);
             if ((charCode < 65 || charCode > 90) && (charCode < 97 || charCode > 122) && (charCode != 8) && (charCode != 46) && (charCode != 32))
             {
               return false;
             }
             else
             {               
               if((evt.value.length <= 1  && charCode == 32) || (evt.value.length <=1 && charCode == 46))
               {
                 return false;
               }
               else
               {                   
                   return true;                 
               }
             }
}