Mouse scroll wheel for skip ahead/back intervals

[titoj]

There are several posts in the Mac and feature requests fora on this subject, but I haven't seen an answer to the following question:

While watching movies, using the mouse to skip ahead or back gives me a skip of 2.5 minutes or so per click of the wheel. That's unwieldy if, as usually happens, I want to go back 10-20 seconds to reply some dialogue I missed. Can I change this default time? (NOTE: Using the MOUSE only, not the keyboard with the hotkeys and the "very short," "short," etc. time settings). If so, how do I go about it?

Some of the other posts have suggested that the interval changes depending on the length of the video clip. Is that correct? If so, is there any way to get down to a 10-20 second jump in a 2-hour video?

Thank you.

[titoj]

An answer of "can't be done" wouldn't hurt my feelings, if that's the way it is.