Hello
Try this code
Sub Test()
    Dim c   As Range
    Dim i   As Long


    For Each c In Range("B2:B" & Cells(Rows.Count, 1).End(xlUp).Row)
        If c = "No" Then
            i = i + 1
            c.Offset(, 1) = i
        ElseIf c = "Yes" Then
            c.Offset(, 1) = i + 1
            i = 0
        End If
    Next c
End Sub