Multiple Text Box References From A User Form

I recently created a userform. I want the data to be placed into the leftheader, centerheader, and rightheader of the document after the user fills in the required fields. I have made the userform, and I can make the code for it to place one item on my userform in the left, center, or right headers. However, when I try to place more than one item in any of the headers excel deletes the first item and overwrites it with the item that is listed last in the VBA code for that respective header. I am new to VBA (this is actually my first program) so I do not know how to make the first value stay there and simply have the next value placed on the line below it.