I tried to solve this question by making a sample layout. In this sample you can decrease or increase the sliders an adjustable number of steps by the push of the UP or Down button.
Layout:
https://docs.google.com/file/d/0Bz6fp9lmXsR-c0tQc2ZCUEFpaG1UZTNCN21qX09tZ1V5SzRz/edit?usp=docslist_api
i hope this works for you.
Picture:
https://docs.google.com/file/d/0Bz6fp9lmXsR-Rnpvd1N0TXNCaG8/edit?usp=docslist_api
edit : one problem remains, if a slider is on top, it will jump to the bottom when furder increased. The fixing of this is in development by MD.