help with dynamicaly created computed column

how do i make a dynamicaly created computed column persisted?

RCSDataSet.Tables("Invoices").Columns("InvoiceTotal").Expression ="Sum(Child.Total)"

Unfotunately I can't do it in the designer because my vb express will not let me add any aggregates either in the dataset or table designer.

Throws an error: Unbound reference in aggregate expression, 'system,data, aggregatenode'

[821 byte] By [Cammyr] at [2007-12-28]