Command that numbers

[cduke5]

I used to do this but have forgotten the command.
Picture an elevation of a glass building and I need to label and number each piece of glass. If each piece needs to start with "A" then a number I used to array the letter "A" then select them. This is when I would enter "the" command and it would let me pick the order I wanted it to number (order of selection, X, Y). If I selected x it would automatically add numbers across the X axis and I would end up with the glass labeled A1, A2, A3, ...... Perfect.
Jog my memory please.

[cduke5]

Never mind, I remembered.

Tcount

[Organic]

This lisp might be of interest also to you: http://lee-mac.com/numinc.html