How to update serial number from DI API

Halo,

example I want to update serial number like this

update OSRI set IntrSerial = 'BBB' where IntrSerial = 'AAA'

here sample of my code using DI API

Public oItems As SAPbobsCOM.Items
Set oItems = oCompanyDI.GetBusinessObject(oItems)
????
oItems.SerialNum = 'BBB'
oItems.Update

but how do I know I'm in IntrSerial AAA ?

what code should I put in ???? to know I'm now in IntrSerial AAA ?

Thanks

Regards,

Arthur Siwan