How do I link a conditional list in MS Excel Data validation?

[Mig]

Data Data Score Column1 Column 2
Column1 10 20
Column2 11 21
12 22
13 23

I have Column head Data and Data Score. Required information is available
under Column1 and Column2.
Data column is selectable thru Data-Validation List -Column1 and Column2
When I select Column1 in selection list under Data column, I should be able
to select information available under Column1 in "Data Score" column.I need
help in this regard.