Sequentially numbering a field based on two different series
I think I am making this one too complicated. We have a contact id field that needs to be automatically assigned based on two sequential numbering systems. Thus, if the ContactType field is "client", it should be numbered as 1 + the last client value, but if the ContactType field is a "contractor", it must be numbered as 1 + the last contractor value. Is there a way of handling this inside the field definition? Other ideas?
Thanks for the help.