Data validation and If statement

Hello,

I have an issue trying to match If statements with data validation.

I have a cell (A1) with a certain result calculated (e.g.: G0,G1,G2).
In another sheet I have a series of lists created (listG0, listG1, listG2)
I want to create another cell (A2) which is dependent on cell A1 but with options to choose from. something like this:

A2=If(A1=G0;listG0);If(A1=G1;listG1);If(A1=G1;listG2)

I tried and it does not work as an input in the data validation box but it works outside...

Also even if it works and I want to display something if A1 is different from anything in the if statement should i put another parameter in all the if statements?
A2=If(A1=G0;listG0;"NA");If(A1=G1;listG1;"NA");If(A1=G1;listG2;"NA") ????

I know this would be easy if excel had something like an elseif command but it doesnt right?

Cheers