Pick diff pick list as per column value

Sir

i am attaching here with my sample sheet .in which there are 4 sheets -sheet1,2,3,4

sheet2,3,4 have three list in their cell a1

what i want is in my sheet1 if b1=2 then my cell a1 of sheet1 show list of sheet2,similarly if B1 of sheet1 is 3 then a1 of sheet1 show list of sheet3 and similarly for sheet4

plz elaborate how can i do this;;;;;

help me by formula/vba etc...