Trigger Script when Enter and Exit Field

Hi

We are trying to set the Browser Title to be different when the user Enters and Exits a specific field. I have the Script below which should work.  We just need to find out how we can tigeer this when the user Enters and then Exits the field.  Does anyone have any ideas?  I cannot see anything in Workflow which can trigger on Enter/Exit of a field.

Thanks


<script>
function myFunction() {
    document.title = "Some new title text";
}
</script>