javascript in grid databound (code behind)

Question

I have one text box in my grid and need to set validation like should allow numbers upto 

3 digits only 

validation should be done from code behind (grid row databound)

i have javascript its working fine .but i need same js in row data bound 

<asp:TemplateField ItemStyle-HorizontalAlign="Center" ItemStyle-CssClass="assignborder">

    <headertemplate>Interval</headertemplate>

    <itemtemplate><asp:TextBox ID="txtInterval" runat="server" onkeyup="validate()l"></asp:TextBox></itemtemplate>

</asp:TemplateField>

function validate()

{

  //getting key code of pressed key

  var keycode = (key.which) ? key.which : key.keyCode;

   

   var intrval = document.getElementById('ctl00_Mdi_grdabc_txtInterval');

  //comparing pressed keycodes

  if (!(keycode==8 || keycode==46)&&(keycode < 48 || keycode > 57)) {

     alert("Please Enter Digits only");

     return false;

     }

    else

   {

    //Condition to check textbox contains 3 numbers or not

      if (intrval.value.length < 3)

      {

        return true;

      }

      else 

      {

        alert("Interval Should not be greater than 3 digits");

        return false;

      }

    

   }

}