How do tables work?

[Graham Samuel]

Sorry, but I've searched the docs as best I can, including using the 
new search facilities, but I can't find any reference above the 
non-trivial to table objects (or are the fields with table 
properties?), and no cookbook entry. Can anyone explain the table 
properties palette, particularly the bits near the bottom, e.g.

What is meant by 'using'? Is this a place for a formatting string, 
and if so, how specified?

What is the field below this with the 'update' and 'add' buttons?

If I want to script a spreadsheet-like object, can I alter the 
'using' property by script, and if so how (for example, to change 
'decimal' to 'text', which I note is not in the pulldown list in the 
palette).

IMHO it's no good having powerful new features if nobody tells us how 
to use them. But then again, I may have missed something - probably 
have.

All clarifications gratefully received.

Graham
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          Graham Samuel / The Living Fossil Co. / UK & France