I have a column of student ID numbers, a list of indefinite length,
like this:

A
40001
40003
40004
40008
..
..
..

And I just need to create a string from these numbers, comma
delimited, in another cell for use elsewhere. The above would become:
40001,40003,40004,40008.

If the list were not of indefinite length (but not more than, say,
10), it would be very trivial indeed. I can create a dynamic range,
but don't know what to do with it for this application. Any
suggestions for a slick efficient way to get that string via formula?
Or should I just go for a macro to loop through the range?