For Each..Next Loop Issues

Attached is a file that I am having a little trouble with. The Master BOM Sheet has a button to process 20 different Group BOM Sheets based on the Value of the Group Unit Qty. We have been using this file for some time now and I was recently asked to modify the process.

Currently the Process Group BOM Button is linked to UserForm1 which has a ListBox with Group 1 - Group 20. The user double clicks the Group that they would like to process and the form closes. If the user is processing all 20 groups, it gets a little tedious to press the button 20 times and double click each individual Group. I have created UserForm3 with CheckBoxes and an OK button in hopes that if the user checks 3 boxes that the For Each Loop will process all 3 sheets one after another. Here is where I need some help.

If one box is checked, it processes the Group BOM just as UserForm1 Does, but if multiple boxes are checked, it will not process any of them. I also noticed that if I open the UserForm3 and process one Group, then open the form again and cancel out of the form to close it, the data that was last processed gets erased from the Group BOM Sheet.

Right now the sheet code is set to open UserForm3 in the Sub FillLstBox procedure (I left the terminology the same until I get the process complete) when the button is pressed. To see how the process works with the ListBox doubleclick event, change the Procedure to UserForm1.

I had to remove a lot of sheets and additional VBA from this tool to get it on here. If someone wants to see the complete tool to get a better understanding of what is going on, I can send it in Email just let me know.

Really need some help here.