How to create a running index on a field containing text and numbers

We have a column with values like this (USER.F1, USER.F2. USER.F3 ...) for regular integer columns we usually do something like =A1+1 for cell A2 s开发者_开发问答o that it increments appropriately. Will I be able to do something similar for the above column values.

="user.f" & ROW()

or

="user.f" & ROW()-3

should do the trick