I've tried this

Private Sub Worksheet_Change(ByVal Target As Excel.Range)
If Target.Cells.Column = 2 Then
n = Target.Row
If Excel.Range("A" & n).Text = "" And Target.Cells.Text < ""
Then
Excel.Range("A" & n).Value = Now
End If
End If
End Sub

suitably amended, and some others, but can't seem to get them to work.

I want E7 to show time as soon as F7 is <"", E8 to show time as soon
as F8 is <"", etc - for any worksheet in the workbook, not just on
one worksheet.