My app deals with engineering drawings. My program finds the current rev level of the drawing. I need a function that automaticly finds the next rev level. If the drawing change is physicaly changed the rev moves up one letter. If the drawing rev involves a temporary attachment it stays the same letter but a number is attached to the rev level. When a drawing is physicaly changed that has attachments the rev level goes up one letter. Standard engineering practice says I can't use I, O, S, X, Z. When the rev level gets to Y the next rev level is AA then AB etc. Please Help.

Thanks and God Bless,
S. Dyke