How can I add "0's" as additional first digits for numbers in a row
containing 4000 random numbers, i.e. change 1346 to become 01346 and 2345 to
become 02345... and so forth.

If I try "Format cells" and select "Text" I can type the "0" manually cell
by cell and it will be displayed with the "0" as the first digit. However if
I try to use "Edit" and "Replace" in order to automize the insertion of
thousands of "0", it still leaves the "0" out and only displays the number
as it was before. I would be greatful for any ideas.