Hi, while I appreciate the previous answer, as the owner of a Dane....That would have to be one hell of a crate! Ane the chances are they would still wee in it!!! Have you tried Clicker training.....this would involve watching the dog when you thought it was about to wee....then click....a firm no and take them outside encourage them to wee....praise and repeat [knowing a Dane you will need to do this at least 4 million times!!!!]. The theory behind this is that the Clicker attracts their attention more effectively than your voice, which they are too used to. The same effect can be achieved with training discs, a bunch of keys or a small bottle filled with stones. I used training discs to train my Dane to walk to heel, by dropping them on the ground in front of him, getting his attention, correcting him and walking on....reapeat 4 million times etc. There are sites about this type of training, I'll try and find you some.
Hope this helps
Lisa x