Excel 2007 : Creating Multiple dropdown in one cell with Data Validation

Hi All,

I need some help with "Data Validation" in Excel 2007.

I know how to put a list of options in a drop down in a particular cell, however, I want Different set of options in the dropdown of say cell "B1" if value of cell "A1" is changed.

For example:

If Cell A1 has a value "Number" then in cell B1 it should show 1,2,3,4... in the dropdown.
And if cell A1 has "Alphabets" then in cell B1 it should show A,B,C,D....

Thanks in Advance.
Amit.

I Tried that,.. but couldnt make it...