Our kiddos must have the same nasty virus. My toddler has also been suffering since Thursday and then my infant picked it up this weekend. I'm also very frustrated that nothing seems to work (the Immodium didn't seem to offer any relief to my toddler either) I took my infant in to the after hours clinic on Sunday and was given an RX for anti-nausea medicine. (You didn't mention if your daughter is vomiting or not, but if she is, this may make the trip to the doctor worth-while) I took my toddler into his pedi yesterday and was just told to keep doing what we're already doing (no sweets or dairy, make sure he doesn't get dehydrated, switch to soy milk and give him pedialyte, watch the diaper rash - aquafor has been a big help with that) The only new piece of advice I received was to give him lactobacillus (ask the pharmacist for it, it's OTC, but they keep it behind the counter bc it has to be refrigerated). I'm not sure that it's made a difference for my son yet, but just thought I would pass it along if you are, like me, and desperate to try anything!
Good luck to you ... I'm right there with ya!
J.