If x, autonumber, if y x value .1, x value.2 etc

hy guys,
I have this code

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
    Dim myMax As Long, x, ws As Worksheet
    If (Sh.Name = "Master") + (Sh.Name = "Numbers") Then Exit Sub
    If Intersect(Sh.Columns("b"), Target) Is Nothing Then Exit Sub
    If Target.Count > 1 Then
        With Application
            .EnableEvents = False
            MsgBox "You can not change multiple cells in Column B at a time", vbCritical
            .Undo
            .EnableEvents = True
            Exit Sub
        End With
    End If
    Application.EnableEvents = False
    Target.Offset(, -1).Resize(, 20).Interior.ColorIndex = xlNone
    If (Target.Value = "x") * (Target.Offset(, -1).Value = "") Then
        For Each ws In Worksheets
            If (ws.Name <> "Master") * (ws.Name <> "Numbers") Then
                myMax = Application.Max(myMax, Application.Max(ws.Columns(1)))
            End If
        Next
        Target.Offset(, -1).Value = myMax + 1
        Sheets("master").Range("a" & Rows.Count).End(xlUp)(2).Resize(, 2).Value = Target.Offset(, -1).Resize(, 2).Value
    ElseIf (Target.Value = "") * (Target.Offset(, -1).Value <> "") Then
        x = Application.Match(Target.Offset(, -1), Sheets("master").Columns(1), 0)
        If IsNumeric(x) Then Sheets("master").Range("a" & x).Resize(, 2).Interior.Color = vbRed
        Target.Offset(, -1).Resize(, 20).Interior.Color = vbRed
    ElseIf (Target.Value = "x") * (Target.Offset(, -1).Value <> "") Then
        x = Application.Match(Target.Offset(, -1), Sheets("master").Columns(1), 0)
        If IsNumeric(x) Then
            Sheets("master").Range("a" & x).Resize(, 20).Interior.ColorIndex = xlNone
        Else
            Sheets("master").Range("a" & Rows.Count).End(xlUp)(2).Resize(, 2).Value = _
            Target.Offset(, -1).Resize(, 2).Value
        End If
    End If
    Application.EnableEvents = True
End Sub

If i put "x" in column B from Sheet1, Sheet2, Sheet3 then in column A is allocated a unique number and is copied in sheet Master. Is possible to implement in this code next request :if i put "y" in column B, then in column A is allocated "x" value.1 (x.1,x.2,x.3 etc) ant copy in Master?

i will give an example in sheet3