Accessing an Excel Form procedure from a UserForm

In my excel spreadsheet, I have a ListBox which I would like to populate based on values inputted in a UserForm I have made, but I can't figure out how to do this.

To clarify, I have a sub that will add items to this Excel ListBox (Private Sub AddItemsToListBox). When the user selects a value from a UserForm I have created, I would like to call AddItemsToListBox so that the value that was selected will be added to the ListBox.

I tried creating a sub in a regular module, and using Application.Run in my UserForm code, but obviously it won't recognize the ListBox as an object.

Any help would be greatly appreciated!

Thanks.

Hello ExcelHelp...

I hope I understand your question!
Try this workbook and let me know if works!

Thanks very much for trying, but I don't think I explained myself very well.

I want the list box to be in the Excel Spreadsheet, not in the userform. I attached an example that might clarify what I mean.

I want to type something in to the text box and then hit "Add Item to List Box1" and have it add to the data in the listbox on Sheet1.

If anyone knows if this is just not possible, that information would also be really helpful. I'm totally stuck.