I solved it!!
On screen 2 in frmMain set the item to frmMain.LastSubmit. Going to post the working app in community section.
The attached app (zip file) has 2 sreen and 2 lists. Click a big "+" on screen 1, takes you to form on screen 2. There you complete top part of form to add parent (one field). Go to the 2nd form on screen and add related item(s) 2 fields on text for your item and the other drop down to make relation to parent. Between the forms is a datatable that should populate with the child information as you add it. That doesn't work. I can't figure out why. Can someone please take a look? I appreciate your assistance. Additionally I will place the completed app in the "Community Section" of this site for others to learn from.
Solved! Go to Solution.