WPF Combobox Dual Bind

Recently start to learn WPF and am struggling with some of the concepts, especially databinding and comboboxes.
I have the following 2 tables:
provTable
provID
provName
cusTable
provID

By using the datasource wizard I have add the datasource to my program and dataSet.
By dragging the cusTable onto form I have the fields showing the records and created save and navigation buttons.

By default the comboBox is showing the correct provID according to the records selected, im under the impression it binds to the cusTableViewSource.

How do I now keep the comboBox binded to show me the value but instead show provName and also in the list of items all the provNames?
I have tried several tutorials and changing the itemsource and displaymemberpath, it works to show all the names in the provTable but then isn't bound to my selected value in cusTable anymore.

Any recommendations or help please.