Keybinds in openbox / moving windows

Hey
Does anyone know if there's a way to change the "sensitivity" of an <action name="Move"> or <action name="Resize"> entry in openbox? My mousebind (A-Left, A-Right, + Drag) works as expected, but I'm specifically after something for the keybind.   I'm completely doubtful, but optimally I'd like to be able to smoothly resize or move windows by keypresses, rather than in jumps, and specify a speed, but, yeah...
Thanks for any help (or suggestions to radically change the way I'm approaching this)