|This process will allow the user to enter data in Column A just once:|
1 - Select Column A
2 - Click Format...Cells...Protection Tab
3 - Uncheck the Locked option
4 - Click Tools...Protection...Protect Sheet
5 - Set Password to the word secret
6 - Click the Sheet tab for the sheet and paste this code into the window that opens:
Private Sub Worksheet_Change(ByVal Target As Range)
'Determine if change was to Column A
If Target.Column = 1 Then
'If yes, Unprotect sheet
'Locked changed cell
Target.Locked = True
When the user enters data in Column A, the code will Unprotect the sheet, Lock the cell that was changed and Protect the sheet again.
You should also Hide and Password Protect the code so that the user can't see/changed it.
If you need to know how to do that, let us know.