I have several spreadsheets with data listed in 4 columns. Each column has
about 1500 rows of data. I need to reorder my data so that column B's data
is placed underneath the last data entry in column A (with column C under B,
etc.)

e.g.

existing order

A B C D
1 1 1 1
2 2 2 2
3 3 3 3
4 4 4 4

new order

A
1
2
3
4
1
2
3
4
1
2
3
4
....

Any suggestions would be very much appreciated.