Are these two forms open at the same time? You can have two forms communicate with each other but they must both be open at the same time. It is complicated and unless you are code savvy I woudl not go down that path.
It might make more sense to calculate the costs in Form1 and export the data from form 1 then import that data into form2. Then you will have the data locally in form2 and you can do what you want with it.
Paul