The present invention regards system and apparatus for selectively and accurately deploying one or more sequentially positioned medical appliances from a portable medical device. The apparatus includes a body having a channel, a string passing through the channel, and a mechanism for moving the string a predetermined first distance to deploy a first of the medical appliances and for moving the string a predetermined second distance to deploy a second of the medical appliances. The medical appliances may be, but are not limited to, ligating bands.