Compare multiple TextField through javascript

this code not allow the same text in any two text field

 function comp_txt(present)

  {

    dml=document.forms['aspnetForm'];

    var i;

    var per=document.getElementById(present);

    for(i=0;i    {

        if(per.name == dml.elements[i].name)

        {

        }

        else if(per.value == dml.elements[i].value)

        {

            per.value="";

        }

    }

  }

you can call on onChange event and pass argument id of current

text field