If you're using the ARP (Automatic Row Processing) you can simply set the corresponding Format Mask attribute (under the Appearance section).
E.g. for a currency, you could set "FML999G999G999G999G990D00". Then you could save either "$100", "100", "$100.00" or "100.00".
You can test this easily using the Sample Database Application with the Products page.
Hope this help
Thanks Max. I've been using the legacy builder which does not format numbers as numbers. It essentially changes the number to a string, or else you would be able to commit.
I note that the formatting works only on database items. If you have an item with the value selected via a sql query, you have to do the formatting with a to_char in the query, e.g., "select to_char(money,'$999,999,999.99') from whereever. Please let me know if there is a better way to format non-database numeric values.