in keydown fuction confirm box work twice

in keydown fuction confirm box work twice


hello

in keydown fuction confirm box works twice. how to prevent this .
below is the sample code . 

<input type="button" class="button" value="Cancel" id="can_bt" onclick =" cancel1 ('<?php echo $i; ?>','<?php echo $_POST['ntr']; ?>')"   onkeydown="exeClick(event)"  />


function exeClick(e){
 
       var eId=$(e.target).attr("id");
       if(e.keyCode==13)
        {
           $("#"+eId).click();
           return true;
        }
}


function cancel1(no,ntr){
    
    var msg=confirm("Do you want to cancel This");
    
    if(msg){
        
        oTable.fnClose(ntr);
    }
    
}


 pls help 
thanks & regards