Formula to replace single spaces only?

Hi All,
Is there a way to replace single spaces with another character in text strings, whilst ignoring spaces that are greater than a single space?

I have a text file that I want to tabulate and the easiest way I can see would be to replace the single spaces, then trim the remaining spaces so that they can be used as the column separators.

Thanks in advance,
Matt

Cheers XLent! Works perfectly and does exactly what I want it to.

Was messing on for an age trying to work it out and now I see it written down it seems obvious.

Thanks again,
Matt