[dba-SQLServer] RepServices: Binding a table to a StoredProc

Hi All
I have a table on an RS report

When the table is bound to a simple Select statement EG select * from
Customers
I can then further bind each control on the report to a field in the
recordset.

EG I select the relevant text box - then from the property sheet I select
from the list of available fields
in the 'Value' combo box on the property sheet

EG txtCustomer value in the property sheet = Fields!CustomerName.Value
Cool

But when I change the recordset for the table to a Stored Proc
I see no available fields when I select a Text box and try to bind it to a
value in the propertyy sheet
Infact rather than a list of available fields, all I can see is <Expression> 

Don't know where to go from here - any suggestions appreciated

Many thanks

Darren