|This Worksheet_Change macro will multiply the entry by 1000.|
As written, it will work for Column A only.
Right-click the sheet tab where you want this happen, choose View Code and paste the code into the pane that opens.
As always, test the code in a backup copy of your workbook since macros can not be undone.
Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = False
If Target.Column = 1 Then
If WorksheetFunction.IsNumber(Target) Then
Target = Target * 1000
Application.EnableEvents = True
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