Our application works very similar. 
We work with seperate print jobs and merge the results in our own preview.
This way we can show the preview asynchronous, while generating.
A possible solution to this would be to add duplicates of the “.lst” to achieve the same result.
This way you can print all kind of combinations.
And According to my information, it is possible to change the datasource (with seperate records) in every “NextCombinationPrintStep”-Event, depending on the next “.lst”-File.
LL.DataSource = GetMyDataSource();
LL.AutoProjectFile = @"invoice1.lst;toc1.lst;invoice2.lst;toc2.lst";
LL.Print();
But this way you get a “complete” Numbering through everything.
It would be great to have a Method ResetPageNumber() in the “NextCombinationPrintStep”-Event for more flexibility. I will open a sperate Topic for this:
ResetPageNumber() in the “NextCombinationPrintStep”-Event