Problem with If Statement
 

Hi
I have got a problem with an If Statement that I am trying to create.
Cell A1 is a variable number (but I will use -24, for the example)

A3 = -9
A4 = -15
A5 = -3
A6 = -11
A7 = -7
A8 = -1
A9 = -13
A10 = -5
A11 = -17
A12 = -4
A13 = -6
A14 = -14
A15 = -12
A16 = -10
A17 = -2
A18 = -16
A19 = -8
A20 = -18

The formula that I need to create is basically the following that I need to
nest together.
If Cell A1 is higher than -18 (this is lower in negative form, -19 etc)
=IF(A1<-18,IF(SUM(A3-18)=A1,2,IF(SUM(A3-18)<A1,0))
If Cell A1 is Lower than -18 (this is higher in negative form, -17 etc)
=IF(A1-18,=IF(A3=<A1,1,IF(A3A1,0))

The final pieces of the Jigsaw a
If Cell A1 is equals to 1.
=IF(And(A1=1,A3=-18,-1,0)
If Cell A1 is equals to 2.
=IF(And(A1=2,A3=-18 or -17,-1,0)
I hope that this makes sense

Thanks