Newbie: Solution?

Hello Experts,

A sum (manually entered or just a calculation field) must sprats into
several small amounts. the sum entered to a database firstly; an error
message is required to appear while you key in the last small amount, in
case the total figure of the several small amounts is not equal to the
sum entered before. You can't expect how many individual small amounts
will be input to a same/different database. For instance, you have a
monthly budget to spend but yet not know how many particular expenses
will occur in the later days, and you always pay out exactly all the
money.

Thanks a lot for your kind help!
Walter