data validation : List , data from single cell conatining (multiple values) VALUES

Friends, can we apply data validation: list from a single cell containing many values...

e.g A B C............
1 12,24,36,48 (in 1 cell) now referring to a1 cell data in C1, using data validation List: data must be 12
24
36....
i tried to use nested formula.... doesn't worked.... if possible then your advice is needed