Calendar control -2003/11.0 weirdness

[musclpete]

I have a VBA form that I added 2 text boxes to determine a date range. In those boxes, it calls a calendar control that's initially invisible. Here's the code:

Dim sWhere As String
Private Sub tbFrom_MouseDown(ByVal Button As Integer, ByVal Shift As Integer, ByVal X As Single, ByVal Y As Single)
cal1.Visible = True
sWhere = "From"
End Sub

Private Sub tbThru_MouseDown(ByVal Button As Integer, ByVal Shift As Integer, ByVal X As Single, ByVal Y As Single)
cal1.Visible = True
sWhere = "Thru"
End Sub

Private Sub cal1_Click()
If sWhere = "From" Then
tbFrom.Text = cal1.Value
Else
tbThru.Text = cal1.Value
End If
sWhere = ""
cal1.Visible = False
End Sub

What's not happening is when I 'mouse down' over either of the text boxes, the calendar doesn't come up. If I click in the area where the calendar control is located, then it selects a date even though I can't see what date I'm selecting. From then it works as expected.
What am I missing? I've tried to put the same code in "dbl-click" and "change" and still get the same result.