Allrighty then; I can get a bit more advanced
In the lower-left corner of your screen, just below the time slider, is a white box; that is the command line. Click in there, and type the following:
move -a -_ _
Before you go nuts with that, here are a few notes:
1) DO NOT type underscores in the command line; I merely put those there becase they are variables that YOU must decide.
2) Replace the first underscore with either x, y or z, depending on which axis you want to move your selection along.
3) Replace the second underscore with any number; positive or negative. Decimals are allowed.