Join text in userform textbox

[jeffreybrown]

I'm a little stuck here. On sheet1, I would like the user to double click on one of the task in column B and then have a userform display the associated tasks from column C. I have the double click and userform already built, just looking for some help to retrieve the sub task into the textbox on the userform. I can see this one of two ways. Either all of the sub tasks from column C are written into the textbox on the fly, or, have some textjoin function written into the cell (D2) on the fly and then that is read into the textbox. After the user closes the textbox, I would remove the textjoin in the cell. For the textjoin function, I'm not sure how to get in to be dynamic to all of the other cells.