Thnak's for helping me out with this. Well I am trying to build a user form where it takes value from text box for size D and one for length L and I choose a process in a combobox like size, straightness, circularity and cylyindricity which have different formulas and are associated with each other. So when I enter a size and length and choose a process and hit the command button I want it to calculate the value. So D is a constant and ts, ci, cy are all results which I want to be able to calculate . I am not sure if you understand what i am trying to do? But i could use some assistance on this.