You could use a sequence of wildcard Find/Replaces, where:
Find = [ ]{2,}
Replace = ^32
Find = [ ^13]{1,}
Replace = ^p
Find = [^13]{1,}
Replace = ^p
This will reduce all repeated space & paragraph sequences to one of each, then reduce and combined paragraph/space sequences to just a paragraph break. At worst, you'll be left with cells that have a unnecessary paragraph break in the last paragraph before the end-of-cell marker. No need for VBA, though you could record the above as a macro.

What's not clear, anyway, is what you'd want to do vis-à-vis paragraph beaks and end-of-cell markers.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]