One of the things that I find common is that you don't fill the child form's parent property and therefore anything containing oCallingForm will give you an error. Another thing to look at is the fact that you may not be saving your field value to nUnlockValue property (or whatever the property was). I would put my debuging skills to work if I were you and make sure all this is happening. If it's working the way you said it should be before you click on the save button make sure these properties do exist. Turn on your debooger and check it out!

Do your analysis and design before you start writing code and separate your tiers - it'll save alot of heartaches in the long run.