Input form with criterion-based selection list

Hi Guys,
Thanks to the great help I was able to build the attached application. It's purpose is to keep track of take-offs and landings for our gliding club.
I am happy with the way I can add flights (using the button "Add flight") in the list now and I am now turning to a nice way to register landings.
I have implemented a macro that just puts a timestamp in the active cell and that works OK. I can use it to register the landing time.
However, I'd like to make it more fancy. I would like to have a button called "Close flight". When pressed a form or a window should appear with all open flights (i.e. all rows in the spreadsheet that are not empty but have no landing time, that is cell in col. G is empty). The user should then be able to select one. Press on a button called "Now" or enter a time manually which then is put into the spreadsheet.

Maybe a complicated story, but the attached example should make things clear.

Anybody care to help how I should achieve this?

TIA