Adding a calculated column to datatable based on Parent field.

Hi,
I'm trying to create a calculated column in a datatable which puts in the value of a field from a parent table.
I'm working with the following tables from my db: custOrders, Customer
Essentially I just want to bind a combo box to the customerName field which is Parent in the relation with custOrders.

Code:
'Add Relationship
r = New DataRelation("Customer-custOrder", ds.Tables("Customer").Columns(0),                                                 ds.Tables("custOrders").Columns(1))

ds.Relations.Add(r)

'Add Column
ds.Tables("custOrders").Columns.Add("cName", GetType(String), "Parent(Customer-custOrder).customerName")

'Add Binding
lblCust.DataBindings.Add("Text", ds, "custOrders.cName")

The problem is with "Parent(Customer-custOrder).customerName"
It complains when I try to specify the relationship name (like I have here). If I have only one parent relationship on the custOrders table then I don't need to specify the relationship name and it works - but I have more than one parent relationship.

The error is:
Syntax error in Lookup expression: Expecting keyword 'Parent' followed by a single column argument with possible relation qualifier: Parent[(<relation_name>)].<column_name>.

I have tried putting the relationship name in quotes and I get the same error.

Is there a better way to bind to the parent field, or how can I get the column add function to work?

Thanks