In Excel 2007, in column C I have some cells that contain numbers and some
cells that are blank. In column D, for every blank cell in column C I need
to return the cell reference of the previous cell containing a number. For
instance, if C10 is 5, c11 is blank, and c12 is blank, then i need d11 to
return "$C$10" and I need d12 to also return "$C$10". D10 should be blank
since C10 contained a number.

In column E, I need to do the same thing except I need the next non-blank
cell returned rather than the previous.