I thought this would be easy but nothing ever is, for me anyway.
I used Dlookup when the form opens to read the perameters values stored in a table. No problems.
Sometimes the user makes silly typos like 1/2/2011 when the range is between 2013 and 2014
When he runs the report date to date the records never show up.
Note the date layout may seem strange I live in Australia. Beautiful one day, perfect the next. (Except for fires and floods)

Private Sub IsDate_BeforeUpdate(Cancel As Integer)
If IsDate < StartDatePerameter OR IsDate > EndDatePerameter Then
MsgBox IsDate & vbNewLine & "Date Is Out Of Range"
     Cancel = True
     Me!IsDate.Undo
End If
' does not work
End Sub

So I hard coded the dates to see if that worked. It did not

Private Sub IsDate_BeforeUpdate(Cancel As Integer)
If IsDate < "#1/7/2013#" OR IsDate > "#30/6/2014#" Then
MsgBox IsDate & vbNewLine & "Date Is Out Of Range"
     Cancel = True
     Me!IsDate.Undo
End If
' does not work
End Sub

Finally I tried something I have never come across before DateValue()

Private Sub IsDate_BeforeUpdate(Cancel As Integer)
If IsDate < DateValue(StartDatePerameter) Or IsDate > DateValue(EndDatePerameter) Then
    MsgBox IsDate & vbNewLine & "Date Is Out Of Range"
    Cancel = True
    Me!IsDate.Undo
End If

' IT WORKS. Access evaluates correctly
End Sub

I hope this may be of help to someone
Regards Alan Hill

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Reply from Richard Rost:

Thanks for sharing. Looks like your parameter values are being treated like strings. DateValue converts them to actual date values. I use the CDATE() function which works very similar. The reason why your hard coded values didn't work is because you used quotes TOO. Just: #1/5/2001# not "#1/5/2001#"