A very handy xBase expression to know is the COUNTER() function.
When you invoke the COUNTER, it returns a sequential number based upon the parameters you give it.
Go ahead and bring up your expression tester in GoldMine (CTRL-SHIFT-D).
Try this: COUNTER("MyCounter",1,1).
The first parameter is the name of our counter. This can be whatever we want. ("MyCounter").
The second parameter defines how large our increment should be. A value of 1 increments by 1, a value of 10 increments by 10.
The third parameter specifies where our counter should start. Typically this is set to 0, however, if a numbering scheme is already in place, this can help generate the right numbers for your sequence.
ProTip: This is a great expression to include in a Lookup.Ini for new contact records.