Condition fields to amounts

Hello

I'm new to Sugar.

I solicit your help on my problem below.

I have a field A, a field B, a field C and a field D which are in currency.

1) I would like field B not to appear if field A is greater than 0 and if field D remains at 0 (formula to be entered once the “dependent” box is checked).

2) Conversely, I'd like field C to appear if field A is filled in.

What would the formula be? I know how to do it when lists are present with isinlist, but not with amounts.

Thanks in advance for your help :)