set BoxObject position from code

hi ppls
can somebody tell me how to set BoxObject or TextObject position in crystal report from the code
I try something like this
Dim cet As New CrystalReport4
Dim SampleReportText1 As CrystalDecisions.CrystalReports.Engine.BoxObject = CType(cet.ReportDefinition.ReportObjects.Item("Box1"), CrystalDecisions.CrystalReports.Engine.BoxObject)
SampleReportText1.Top = 100

but i get some error: Invalid object type

Thanks for your time

Are you using VB.NET?