定位光标与值的写入或删除

 function insertchr(txtboxID,text) {
   txtboxID.focus();
   var workRange=document.selection.createRange();
   if (workRange.text!=null){workRange.text="";}
   txtboxID.select();
   var allRange=document.selection.createRange();
   workRange.setEndPoint("StartToStart",allRange);
   if(workRange.text!=""){
        workRange.text+=text;
        workRange.collapse(false);
        workRange.select();}
   else{
        allRange.text+=text;
        allRange.collapse(false);
        allRange.select();
   }
   }

function delchr(txtboxID) {
   txtboxID.focus();
   var workRange=document.selection.createRange();
   if(workRange.text!=""){
       workRange.text="";
       workRange.select();
       return;
    }
   txtboxID.select();
   var allRange=document.selection.createRange();
   workRange.setEndPoint("StartToStart",allRange);
   if(workRange.text!=""){
        workRange.text=workRange.text.substr(0,workRange.text.length-1);
        workRange.collapse(false);
        workRange.select();
    }
   else{
        allRange.text=allRange.text.substr(0,allRange.text.length-1);
        allRange.collapse(false);
        allRange.select();
   }
  }