I have over 16,000 rows of data. In the first column I need to combine
cosecutive cells. The number of cells to be combined varies. For example, I
may need to combine cells a1, a1, a3, a4 in one instance; cells a100, a101 in
another instance; cells a5200:a5220 in another instance; depending on the
cells in the other columns. The combined cells need to be comma-delimited.

I know I can use =A1&" "&A2 or =concatenate(a1,a2) or =concatenate
(a5200:a5220), etc. However, this is tedious because I have to manually do
this throughout all 16,000 rows.

What I would like to do is highlight the cells that need to be combined and
use a keystroke or two to combine them.

For example,

The first instance of cells to be combined is:
cell a1 = 1245-aw
cell a2 = 5241-ed
cell a3 = 3464-th
cell a4 = 156302-yu

After using the keystrokes, I want the result in cell a1 to look like
"1245aw, 5241-ed, 3464-th, 156302-yu" (without the quotes). There will be
between 2 and 20 cells to be combined, numerous times throughout the
worksheet. Right now I have use cut and paste for every instance to be
combined.

Thank you for your anticipated help.