I have two list boxes for users to select dates, and want to use IsError to
generate a msgbox if the user tries to run the code without selecting a date.
The current code is:

If CDate(lstTo) < CDate(lstFrom) Then
MsgBox "The 'To' date should not be before the 'From' date!"
End If

This covers the user entering the dates backwards, but how do I make this
work if the user omits the dates completely?