LucasD wrote:
Hi,
Here is what I am struggling with:
The table will hold a thousand rows

In one column there is a ref. number between 1 and 50 that I will input

I would like another column to generate a sub-reference in line with the
reference numbers above. So, it would look like:

Column A Column B
1 1.1
2 2.1
2 2.2
3 3.1
4 4.1
2 2.3
3 3.2
1 1.2
2 2.4

and so on. I am thinking that I need to use CONCATENATE but after that am
stumped.
Help gratefully recieved

Assuming your data starts in row 1, put the following in B1 and copy down:

=A1&"."&COUNTIF($A$1:A1,A1)