Took a rest and came back at it fresh and finally figured it out. Not obvious (to me at least) so here's how to do it should someone else stumble upon this post.
In the Form for OrderHeader, go to Properties and click on Data. From the list of fields, add the foreign key field (in this case, OrderDiscountID).
Now go to the DataCardValue properties.Items - LocalOrderDiscount (data source with the values that should be used in the drop down)Value - You should now be able to choose from the fields
Next to the DataType (e.g. 123) there is a drop down. Click this and choose Allowed Values.
Now go to the Advanced properties (for the DataCard) and look under the Data options set the following:
Name the DataCardValue - in my case I used DataCardValueOrderID.
Under Data, set Items to the Datasource to be used from the drop down (in my case, LocalOrderDiscount)
Under Data, set Value to the column you want to display (in my case, OrderDiscountName)
Now go to the properties for the Datacard and check the following:
DataField - Name of the bound field in quotes, e.g. "OrderDiscountID"
DisplayName - Whatever you want the label for the drop down to be
Required - I've left this as false for now
Default - ThisItem.OrderDiscountID (e.g. the bound field name)
Update - DataCardValueOrderDiscountID.SelectedValue (Name of datacardvalue followed by .Selected.Value)
AllowedValues - DataSourceInfo('[Order].[OrderHeader]', DataSourceInfo.AllowedValues, "OrderDiscountID")
So far, this is working for me.
To help folk get started it would really help to have a Wizard or two like those in Access!
Cheers
Paul
