Copy and paste from last record at bottom of column

[jreid]

Hopefully this is a simple question?

I'd like to create a macro that copies the formulas from the last non
empty cells in a group of columns, these formula's I'd then like to
paste into the empty rows directly below, but limit the paste function
to the rows where data exists to the left of the current selection.

For simlicity, lets say I have data in cells a1:a20, but I only have
the associated formulas in cells b1:e1, how do I populate cells b2:e20
with the formulas.

Thanks