Ok, someone give me the skinny - how do I do it, and when is it recommended?

Sahti is 15 months old and has developed a bad habit of having a few sucks in the middle of the night, and then sticking the dummy in for a few sucks, and then back to me for a few more sucks. This can go on for HOURS at a time and I'm really over it, I need sleep! I wouldn't mind feeding her at night if she just fed and then went to sleep, but she just does this over and over and I'm averaging a few hours sleep a night, and its just not enough for me to deal with the other kids as well during the day.

So I thought that I could give her a sippy cup of cows milk or something when she wakes up during the night, or get DH to give it to her (I'm not sure I could express any milk out at this point)

Any tips?