I came across this little program on Milovana - http://www.milovana.com/forum/viewtopic.php?f=2&t=6385
It's little program that you run on your own PC so no net connection needed once set up. It works randomly but allows you to set the parameters as follows
min/max number of days of chastity
min/max period between milkings during the chastity period - optional
min/max number of days off in between
It can also be set to increment the chastity parameters for each fresh session so that it will slowly test you more and more, but you can set absolute values not to be exceeded. The increment function is optional.
The data is stored in a file but is not in plain text so unless someone suitably skilled is willing to crawl over the coding to work out how it is stored so that they can work out how long has been set you just don't know and must simply run the program every day to find out.
Once a session is running it is possible to add days (as a punishment perhaps) and to shift the time frame (ie add days to min & max chastity days) though this will only effect the next session.
Suitable for use alone but probably also a good tool for remote use by busy Dominants - if both sub and Dom/me have a copy on their machines the Dom/me could set the values and just email the "session" file across for the sub to c&p into the relevant folder.