Help needed with expert advisor programming

Hello,
I'm learning programming expert advisor and I'm a bit stuck on this part, so I was wondering if anyone here can help me out. I want to make a code where buy or sell is conditional in the following equation:

Buy
IF(Num1<Num2;(((Num1+Num2+Num3+Num3)/2)-Num3)
IF(Num1>Num2;(((Num1+Num4+Num3+Num4)/2)-Num3)
IF(Num1=Num2;(((Num1+Num4+Num3+Num1)/2)-Num3)

Sell
IF(Num1<Num2;(((Num1+Num2+Num3+Num3)/2)-Num3)
IF(Num1>Num2;(((Num1+Num4+Num3+Num4)/2)-Num3)
IF(Num1=Num2;(((Num1+Num4+Num3+Num1)/2)-Num3)

Can someone help me out and write an example or explain it to me? It will be much appreciated.

Thank you