Count number of instances of an act. #

I have a spreadsheet that has account numbers of the customer for each order they place. I would like to add a column to the left of the account number column and would like it to display the number of instances of the account in the cell in the same row as the first instance of the account (in the new column).


New column ..........Act.#
2 ................... 354
.......................354
4 ...................355
........................355
.......................355
.......................355


Something like that but for 55,000 rows. Any ideas?

Then, using the number in the left column, i would like to automatically run a presaved macro corresponding to that number. Ive got macros 1-12 and i need a macro that will query the left column number and then run the corresponding macro.
Thanx Guys!