Clicking a macro button to add date to a cell in the same row as the active cell

[Raceman]

I need a macro that when a button is clicked, after selecting an active cell in A:, the current date will be put into the same row, column AM.This date will be a time stamp so it shouldn't change when the file is opened the following day.

 

[Momentman]

Something like this

Sub timestamp()
    Cells(ActiveCell.Row, "AM").Value = Date
End Sub