I am building a database of art pieces, and I have a field for Net Sale Price that is dependent on the field Type of Sale, which has three radio button choices from a value list (Private, Auction, Gallery). Depending on which of these three choices is made, Net Sale Price needs to pull figures from one of three fields: Private Sale Price, Winning Auction Bid, or Gallery Sale Price.

 

It seems I need to use the Evaluate function in the Net Sale Price field calculation, but I need a little "kickstart" here... ;-)

No, you need to use the Case() function:

Case (
Type of Sale = "Private" ; Private Sale Price ;
Type of Sale = "Auction" ; Winning Auction Bid ;
Type of Sale = "Gallery" ; Gallery Sale Price
)