edit space between characters

I created simple "text on face" in "Modeling" application. Now I need to edit space between characters, but cannot find, how to do it. When I change parameters "offset" or "W Scale", also text size is changed. Do you have some suggestion, how to do it? But please, keep in mind, I need create lot of text, so create each character separately is too time consuming.

Attached is image with example.