DataGrid with more than one data source

Hi,
I have run into a small problem here...
I have a usercontrol with a datagrid - this datagrid has a datasource, lets call it SourceOne.
Now, within this grid I have a custom cell template and in this I have a combobox that needs data from a different source, SourceTwo. BUT it only uses SourceOne which is assigned to the parent grid. The combobox must bind to true/false values converted to textual values using an IValueConverter. Is what im trying to do possible?

Are sourceone and source two different classes? How about the binding of your controls? Do you have a xaml markup that you can post?