|This might get you started. Paste this macro into the Sheet module for the sheet in which you want the dates inserted. (Right Click the sheet tab and choose View Code, then Right Click...Paste)|
The code will monitor the sheet and if a change is made in Column A, it will check for an A, B or C in the row that was changed and insert a date in Column B based on what it finds. As written, if anything other than an A, B or C is entered in Column A or if more than one cell is changed at the same time or if the value in Column A is deleted, the code will do nothing.
Private Sub Worksheet_Change(ByVal Target As Range)
'Do nothing if more than one cell is changed or content deleted
If Target.Cells.Count > 1 Or IsEmpty(Target) Then Exit Sub
'Determine if change was made to Column A
If Target.Column = 1 Then
'Enter Date in Column B based on entry in Column A
If Target = "A" Then Target.Offset(0, 1) = Date + 1
If Target = "B" Then Target.Offset(0, 1) = Date + 3
If Target = "C" Then Target.Offset(0, 1) = Date + 7
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