Try

RELEASE BAR 1 OF file 
DEFINE BAR 1 OF file PROMPT "This is a test" BEFORE 2

>I want to change the text of a menu bar.
>
>It started out as:
>

>DEFINE BAR 1 OF file PROMPT "Test"
>

>
>In my ON SELECTION routine, I have:
>
>

>DEFINE BAR 1 OF file PROMPT "This is a test"
>

>
>Problem is that the new text is truncated bacause the width of the
>popup is that of the widest bar before this was run.
>
>How do I fix this?