Yes, it is possible to run an event when a value is entered in a cell
Just call the required macro for the OnChange event for the cell.

example:

Private Sub Worksheet_Change(ByVal Target As Range)
If (Target.Row = 1 and Target.Column = 1) Then
call your_macro
End If
End Sub


The above code has to be put in the VBA module for the sheet concerned
And the code will work for cell A1 as you can see from line 2 where th
check is made for changes in Target.Row = 1 which means row 1 an
Target.column = 1 which means column A

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