var currentCharCount = 0;
var maxKeys = 500;

function txtOperationsEdit_keyup(what){  
  currentCharCount = what.value.length;    
  if(currentCharCount > maxKeys){
    what.value = what.value.substring(0,500)
    currentCharCount = maxKeys;
    alert('Error: Too many characters. Max. limit: ' + maxKeys);
  }
  document.getElementById('txtOperationsEdit_CharCount').value = currentCharCount;
}

function checkTextLength(){
}