I figured it would be possible to take the two value's and combine them by sitcking them into a hidden field.
Fname = document.form1.FirstName.value;
Lname = document.form1.LastName.value;
document.form1.CONTACT.value = Fname + " " + Lname;
Then call the function with onchange on your lastname field <input ID="LastName" value="" onChange="populate()"
I'm completely full of cold at the moment so my brains not firing on all thrusters.
Would this require any library like jquery to work?
Appreciate any help.