Can somebody help me out with the following trouble:

I want to have an IsBlank type of feature and want the cell "A2" to be
reflecting a serial number (e.g. A1 + 1), but ONLY and ONLY if ANY of the
other cells in row 2:2 is not blank.

In other words, once you enter any data in the corresponding row, the cell
in column A:A records a new serial number.

MACROS or any other means are most welcome.

THANX