Hello, I am using Excel 97 for windows and working with data validation, settings,allow:list

I am trying to do the following

In one cell, the user selects from a list created via validation. For example, the cell will have a pull down list that gives the choices "A", "B", "C", "D", etc

Then, in another cell, based upon which choice was selected above, a pull down list via validation should appear that is unique to the choice selected above. So, if "A" was previously selected, then in this cell, a validation list would appear with various choices based upon choosing "A" previously. For example, if "A" was selected previously, then in this cell, a validation list would appear that has the values "100,200,400,500" to choose from. If "B" was selected previously, then this cell would have the values "100,200,750,900,1200,1500,etc." to chose from. I have my data arranged in various columns, but I do not know how to get the second cell to choose the proper column based upon the first cell's selection

How do I create the entry for the second cell which will choose a list based upon a previous cell's entry ? I have tried to enter a formula under "data validation/settings/allow:list/source" but it won't accept a formula (if/then statement)

Any help would be greatly appreciated. Thanks.