Conversion from type 'DBNull' to type 'String' is not valid.

Private Function CheckIfOccupationExists(ByRef rstIn As ADODB.Recordset, ByRef cTestOcc As Object, ByRef cTestType As String) As Boolean

        Dim lTestOccFound As Boolean

        lTestOccFound = False
        'UPGRADE_WARNING: Couldn't resolve default property of object cTestOcc. Click for more: 'ms-help://MS.VSCC.v90/dv_commoner/local/redirect.htm?keyword="6A50421D-15FE-4896-8A1B-2EC21E9037B2"'
        If Len(Trim(cTestOcc)) = 0 Then
            lTestOccFound = True
        Else
            'UPGRADE_WARNING: Use of Null/IsNull() detected. Click for more: 'ms-help://MS.VSCC.v90/dv_commoner/local/redirect.htm?keyword="2EED02CB-5C0E-4DC1-AE94-4FAA3A30F51A"'
            If Not IsDBNull(cTestOcc) Then
                rstIn.MoveFirst()
                Select Case cTestType
                    Case "r", "m", "d", "I"
                        'UPGRADE_WARNING: Couldn't resolve default property of object cTestOcc. Click for more: 'ms-help://MS.VSCC.v90/dv_commoner/local/redirect.htm?keyword="6A50421D-15FE-4896-8A1B-2EC21E9037B2"'
                        rstIn.Find("Occ_code=" & cTestOcc)
                    Case "D"
                        'UPGRADE_WARNING: Couldn't resolve default property of object cTestOcc. Click for more: 'ms-help://MS.VSCC.v90/dv_commoner/local/redirect.htm?keyword="6A50421D-15FE-4896-8A1B-2EC21E9037B2"'
                        rstIn.Find("Dep_occ=" & cTestOcc)
                End Select
                lTestOccFound = Not rstIn.EOF
            End If
        End If
        CheckIfOccupationExists = lTestOccFound

    End Function