I need a formula that will return the correct percentage where there is 4
scenarios of comparing Actuals as a percentage of Plan. eg

Actual Plan
110 100
90 100
-10 100
-90 -100
-110 -100
50 -100
10 0
-10 0

I have tried several formulas but they do return the correct answer in all
cases.
Any suggestions would be appreciated. Many Thanks