In this instance, I would recommend using 2 date parameters.
One parameter is your start date, one is your end date. Frequently for me, this is the correct solution.
Create a calculation ([Date field 1] AND [Date field 2] >= [Date Parameter 1]) AND ([Date field 1] AND [Date field 2] <= [Date Parameter 2])
If you are only analyzing one year at a time a single parameter would probably do the trick.
You could create new measures based on the parameter.
Signed Amt: if [date parameter] = [signature year] then [net signed amount]
Approved Amt: if [date parameter] = [approved year] then [approved amount]