Me.Text1Box1.Text = "Test"

  Dim Obj As Object
  Dim TPages As Object
        For Each TPages In Me.TabControl1.TabPages
            If TypeOf (TPages) Is TabPage Then
                For Each Obj In CType(TPages, TabPage).Controls
                    If TypeOf (Obj) Is TextBox Then
                        If CType(Obj, TextBox).Name = Me.TextBox1.Name Then
                            CType(Obj, TextBox).Text = "TextBox1-Text"
                        End If
                        If CType(Obj, TextBox).Name = Me.TextBox2.Name Then
                            CType(Obj, TextBox).Text = "TextBox2-Text"
                        End If
                    End If
                Next
            End If
        Next