Some questions from a novice user.

Here is the task:

I have a workbook with two spreadsheets. Sheet2, column A consist of x cells
of unique serial numbers.
From Sheet1 the user should select an empty cell in column A, then click a
button that starts the UserForm. The UserForm should have a ListBox
populated with the unique serial numbers from Sheet2.
By selecting one serial number (and clicking the OK button in the userForm),
that number should be pasted in to the cell that was active when the
UserForm was activated and the unique serial number should be removed from
Sheet2.

Questions:
- How do you fill up the list box whit the values from Sheet2 when you don't
know the numbers of cells used?
- How do you paste the number chosen into the active cell of Sheet1?
- How do you delete the chosen number from Sheet2?

Any help is appreciated.

Regards
Stein Kristiansen