Elania,
What Bill said is correct, but not the complete story. Many times, I effectively have different equasions for different rows in JMP. However, using JMP's terminology, they are all contained within one formula. The following is a completly ligetament formula, with different equasions being used on 2 different cells.
If( Row() == 1, :x + :Y );
If( Row() == 2, :x - :Y );
Typically, one does not use the row number as the flag for what formula to use, but rather something like:
If( :Sex=="F", :x + :Y );
If( :Sex=="M", :x - :Y );
Also remember, that a formula in JMP can be of any level of complexity. You may find that your data is layed out in a less than convenient format, and changing it's structure might make it easier to use JMP formulas, or you may be able to solve you issues with something like the examples I provided. I do know, that JMP should be able to handle any issues you have.
Jim