Multiply Dependent One Cell Formula

All to occur in cell G2

Condition 1.
If F2 is > 0 then multiply F2 by D2.

Condition 2 in the same cell.
If the product of F2 multiplied by D2 is > E2 AND the sum of F2 and F1
multiplied by D2 is > 0, then add the product of D2 multiplied by the sum of
F1 and F2 to E2, otherwise input E2

Condition 3 in the same cell.
If the product of F2 multiplied D2 is < E2 BUT the sum of F2 and F1
multiplied by D2 is > 0, then input the product of D2 multiplied by the sum
of F1 and F2.

Condition 4 in the same cell.
If F2 < 0, and the sum of sum of F2 and F1 multiplied by D2 is < 0, then 0.

This is the best way I could think of the write out my intention. I think if
I can get the above scenario into a one cell formula that should resolve my
pain.