Runtime parameter passing to Access project report

[VictoriaWass]

I have an Access report whose source is an SQL server stored procedure. This stored procedure has a parameter to which a value must be assigned. Rather than have the automatic message box appear prompting for this value when the report is run, I would like the report to automatically pick up the value from a text box on the form when it runs. Surely this should be obvious but I can't see it, this is all I've managed so far and it is not working...

DoCmd.OpenReport "rpt_confirm", acViewPreview, , RecordSource = "dbo.fhsp_order_confirmation @Identifier = " & txt_ident

... where @Identifier is the parameter in the stored procedure and txt_ident is the text box I want it to take the value from.

Any help would be greatly appreciated.... Vicky