|If the original cell is A1, and the target cell is B1, this code will update B1 if you change A1 by a Drag and Drop.|
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address = "$A$1" Then Range("B1") = Target
Right-Click the sheet tab for the sheet you want this to happen in and choose View Code.
Paste that code into the pane that opens.
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