I'm interested in a solution to this question as well, but like NextYearSox, I don't have Right (Indent) as an option - and if I select Right in the Horizontal dropdown, then enter a value under Indent, the justification snaps right back into Left.
You are right, That option is version related. It is available in Excel 2003 but NOT available in Excel 2000. Not sure what version it first appeared in. I would suspect that the custom formatting suggested in one of the other answers is the way to go with earlier versions.