Cursor control within a field

[Severin Swensen]

I am trying to figure out how to save the location of the insertion  
point in a field so that after updating that same field I can leave  
the cursor where it was originally.

I saw something similar in the "Tale of two Revolutions" session  
presented by Robert Cailliau in his Currency conversion demo. As he  
changed the values to convert it updated and left the cursor in the  
same position.

Thanks for the help.
Severin