I am pulling may hair out over this issue. I am following the steps for Chapter 9 Using Date Parameters From SQL Server 2008 Reporting Services and no matter what I do, I cannot get the two and from dates to work with a date picker.

I have entered the following into the Report Properties Code:
Function DateParameter(DateValue As Date) As String
Dim sDateUniqueName As String
Dim SDateKey As String
sDateKey = YEAR(DateValue).ToString( ) _
& RIGHT("0" & MONTH(DateValue).ToString, 2) _
& RIGHT("0" & DAY(DateValue).ToString( ), 2)
sDateUniqueName = " [ID OPEN DATE].[ID CALENDAR].&[" & sDateKey & "]"
return sDateUniqueName
End Function

But when I follow the stop to change the Data Type of the Parameter to Date/Time I get the following error message: "<Default Value 1> Value is not a date or Time and it jumps to the Default Values Tab.

What am I doing wrong !?!?!?!