I'm trying to implement data validation to require the same data to be entered in two different sheets of the same workbook (double data entry reduces errors). Here is a small example (the data structure is the same in each sheet):

ID age rater score
1 10 1 30
1 10 2 40
1 10 3 50

My goal is to set a data validation in Sheet2 so that each value for "score" equals the corresponding value for "score" in Sheet1 (as defined by having the same values for ID, age, and rater in its row). In other words, an error should be displayed if someone types a score other than 30 for the row containing ID=1, age=10, rater=1 in Sheet 2.

Any help would be greatly appreciated. Many thanks!