Hi Marek, the Transform > Scale command can use either distances or a scale factor in it, there is a description of this in the help file here:
http://moi3d.com/3.0/docs/moi_command_reference8.htm#scale

When you are in the Transform > Scale command instead of entering in a scale factor you can pick 2 reference points to establish the scaling. If you want to use a distance instead of targeting a snap point you can use distance constraint to do that. Click on the "d" field in the bottom toolbar and enter in your distance value. That will then constrain your pick point to be at that distance from the scale origin.

- Michael