I'm trying to write some code that will take a value WeekNum, and add it to an array Week(1 To 51), and then associate a value from a Textbox TargDef. Once this has been added to the array, I want to look up the value of the array for the previous WeekNum and add it to a value ProdTarg. I've created this much so far: Dim Week(1 To 51) Dim Count As Integer If TargDef < 0 Then Count = WeekNum Week(Count) = Abs(Val(TargDef)) If Val(Week((Count) - 1)) = 0 Then ProdTarg = Val(ProdTarg) Else ProdTard = Val(ProdTarg) + Val(Week((Count) - 1)) End If End If I am currently receiving the error "Subscript out of Range" for the line If Val(Week((Count) - 1)) = 0 Then Any help will be greatly appreciated!