[Brian]

If I'm understanding your request correctly, you should be able to use the controls on the Cocoa text ruler to do this. Select Format -> Text -> Show Ruler to show it; once it's visible, select the text you want to modify and use the "Spacing" pop-up to change it.

(The above presumes a machine running 10.5; I don't *think* a 10.4 or 10.3 machine will have different options on the text ruler, but I don't have a machine handy to check...)