Very new at this, I have two fields the end user inputs numeric values, the calculations are based on another field populated by a drop down sharepoint list which determines the type of calculation rendered..i.e
Field 1 - $10
Field 2 - $5
Field 3 = NNN (Dropdown list-sharepoint list)
Field 4(Calculation field) - Based on NNN, subtract field 2 from field 1
Rule used: Condition: If field 3 equals "NNN" Action: field 1 - field 2