If then with Then choice

[Cooper1]

I need to create an if then, and I don't know if its possible for a 2 column layout.
For Example, if the entry for column A is "Department of Agriculture (USDA)" then the choice for column B must be one of the selected items, per the list below. To complicate things, there are 15 options for Column A, and depending on the column A selection there may be as many as 17 options or as few as 4.
Can you help?

[TABLE="width: 503"]
<colgroup><col><col></colgroup><tbody>[TR]
[TD]Department of Agriculture (USDA)
[/TD]
[TD]Agricultural Research Service[/TD]
[/TR]
[TR]
[TD]Center for Nutrition Policy and Promotion (CNPP)[/TD]
[/TR]
[TR]
[TD]Farm Service Agency[/TD]
[/TR]
[TR]
[TD]Food Safety and Inspection Service[/TD]
[/TR]
[TR]
[TD]Grain Inspection, Packers and Stockyards Administration[/TD]
[/TR]
[TR]
[TD]National Agricultural Statistics Service[/TD]
[/TR]
[TR]
[TD]Natural Resources Conservation Service[/TD]
[/TR]
[TR]
[TD]Rural Development[/TD]
[/TR]
</tbody>[/TABLE]

 

[VoG]

See if this helps http://www.contextures.com/xlDataVal02.html