Data Validation - on a seperate worksheet

[natetc]

Here is what I'm trying to achieve

Sheet 1 -
Cell A24 =100
That will trigger a drop down list on Sheet 2 to appear
Cell B24 (Formula i'm working with =If(A24=100,Sheet2!H2,)
Sheet 2!H2 = A data validated drop down cell

Sheet 2 -
Has all the options for my drop down list
B2-B18 contains all my values for the drop down

At the end of this I want to create lists for codes 100, 200, 300 and have the drop down lists for those specific codes appear if entered into the code cells.

Thanks in advance for the help!