design studio TEXT_OnFocus not work on line function code

I am in MA43.1, I would like to know the line number when the user click on any text on the line.

I was able to use the following code to find out the line number on any text field, except the line function code.  When the user clicks on function code, it does not show the alert statement.  Is there any way to figure that out??

function TEXT_OnFocus(id, row)
{
  var vCurrentLineNbr3 =lawForm.getDataValue("MAD-LINE-NBR",formState.currentRow);
  alert ("onfocus = " + vCurrentLineNbr3) 
  return true;
}