>I need to know what the previous value was in a field for processing and comparison routines. I assume I can use the TAG property to store the value before entry (using the GOTFOCUS method) and check it in before exiting (LOSTFOCUS). Is that the recommended way?
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Gotfocus is fine. But if ou need to be able to prevent hte user from leaving depending on hte value of the control before changing, you'll need to do this checking in the valid, so you can return .F. if needed.

>I also noticed that the TAG property is usually text... if I am storing a value, such as a dollar amount, do I need to use the STR & VAL routines to convert it or is there a way to get the TAG to be something other than text?

Tag can only hold character data. This is one of the reasons to create a custom control property to hold the previous value. I have a slew of other personal reasons too. I never use tag for anything. I figure if something is important enough to get stored in a property, it is important enough to get its own property. What do you do when you need to store 2 pieces of information. IMHO, better to never depend on tag than to only be able to depend on it sometimes.