Validate Date Entry

I have a ComboBox on a UserForm. One of the fields that I fill in is a date.

After the date is entered I want to check if it's a valid date.

VB:
Private Sub cboEnterDate_Exit(ByVal Cancel As MSForms.ReturnBoolean)
' Make sure a valid date was entered, it must be in the format 2013/10/21.
On Error Goto ERR

'If Not IsDate(cboEnterDate.Value) Then

[Code] .....

ERR:
MsgBox "The date entered is not a valid date", vbInformation
Cancel = True
cboEnterDate_Enter
End Sub

The code:
VB:
'If Not IsDate(cboEnterDate.Value) Then
execute the If routine if I enter the date 2014/03/33

When I enter the date 2014/03/0001 it do not see it as an invalid date and exit the routine.

The code:
VB:
If Not IsDate(FormatDateTime(cboEnterDate.Value, vbShortDate)) Then
send the execution to the ERR routine if I enter 2014/03/33

When I enter the date 2014/03/0001 it do not see it as an invalid date and exit the routine.

How can I get the validation to catch the 2014/03/0001 as an invalid date as well.