Intermittent Performance

[John Dixon]

I have a field "theWord", into which letters are added. If a mistake is made
 upon entry, the user is able to delete the last character of the field by
clicking on a button that contains the script found below... or by employing
the option key at the same time the user can clear the whole field.
 
The problem I have is that the first time I click on the button, a
character is deleted, but the second time I click on the button then there
is no response, until I click for a third time.

I must point out that the cursor does not leave the rect of the button
during these clicks.


 
on mouseUp
 if the optionKey is "down" then
   put empty into fld "theWord"
   exit mouseUp
 end if
 
    put the number of chars of fld "theWord" into charCount
    put char 1 to (charCount -1) of fld "theWord" into fld "theWord"
 end mouseUp
 
 Any ideas why it does not work everytime ?
 
 regards
 

 John Dixon