clearing a field through a variable holding the name of the field

[Curt Ford]

I've got a routine with a number of fields that the user can click  
on. I keep track of which ones they've clicked on with a mouseUp  
handler that includes

put the target into gFirstGuess

At times I need to clear the field referred to by gFirstGuess, but

put empty into gFirstGuess

seems to just empty the variable, not the field itself. How can I  
clear the field that gFirstGuess refers to? Am I missing something  
obvious? Thanks!

Curt