1) Public textdt As Integer - где-нибудь в общем модуле

2) Private Sub Calendar1_Click()
strdt = Format(Calendar1.Value, "dd.mm.yyyy")
Select Case textdt
Case 1
    form1.TextBox1.Value = strdt
Case 2
    form1.TextBox2.Value = strdt
Case Else
    Exit Sub
End Select
Unload CldForm
End Sub

3) Рядом с каждым текстбоксом маленькая кнопочка для вызова формы с календарем:
Private Sub CommandButton1_Click()
textdt = 1
On Error Resume Next
CldForm.Show
End Sub

Private Sub CommandButton2_Click()
textdt = 2
On Error Resume Next
CldForm.Show
End Sub

4) При инициализации формы с календарем:
Private Sub UserForm_Initialize()
Me.StartUpPosition = 0
Select Case textdt
Case 1
    With form1
        Me.Left = .Left + .TextBox1.Left
        Me.Top = .Top + .TextBox1.Top + 42
    End With
Case 2
    With form1
        Me.Left = .Left + .TextBox2.Left
        Me.Top = .Top + .TextBox2.Top + 42
    End With
End Select
End Sub

For i=1 To r.Rows.Count
  If r.Cells(i,1).Value>CDate(TextBox1.Text) AND r.Cells(i,1).Value<CDate(TextBox2.Text) Then
    ListBox1.AddItem r.Cells(i,2).Value
  End If
Next i