Here is one of the solutions. In the Text.Valid event:
if alltr(this.Value)=="F"
this.value="FED EX"
endif

>I was trying to figure a way for a user to populate a field(textbox) automatically but still give the user the ability to change it. Example, if the user types 'F' , the interactive change will kick in and fill out the rest with 'ED EX' so that the word 'FED EX' appears because 90% of the time it will be FED EX but for the other 10%, the user needs to type something else that begins with 'F' but the interactive change only knows about FED EX.