I have code that enters date and time in column E if 100 % (1) is entered in
column D, how do i modify this code to have 1 more timestamp in column F
which would be entered each time i change value in column B?

What i have now is - "task complete timestamp", now i want to add "last time
modified timestamp"

This is the code:

Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)

With Target
If .Cells.Count 1 Then Exit Sub 'one cell at a time
If Intersect(.Cells, Me.Range("D:D")) Is Nothing Then Exit Sub

On Error GoTo errHandler:

If IsNumeric(.Value) Then
'.Style = "Percent"
If .Value = 1 Then
Application.EnableEvents = False
With .Offset(0, 1)
.Value = Now
.NumberFormat = "mm/dd/yyyy hh:mm:ss"
End With
End If
End If
End With

errHandler:
Application.EnableEvents = True

End Sub