You cannot access both recordsets at the same time. Once you call NextRecordset, the previous recordset is closed.
Move the data from the first recordset into an array (see Recordset.GetRows method). Then get the value from the second recordset and finally process through the array.

Or use With Rollup instead of Computed. You will only get one recordset with the following statement

Code:
select CustomerId, test=Count(OrderId) 
From Orders 
group by CustomerId With Rollup
With Rollup creates a total for each group and a grand total. Also check out the Grouping aggregate function.