Instead of use templates you can generate a RDF representation of the spreadsheets and easily transform the RDF data into YARRRML, RML or R2RML.
This can be done manually reading the data and generating the graph with rdflib or you can create a mapping for the "csv" files (each sheet of the spreadsheets) and generate the rdf with tools like RDFizer or RMLmapper.
I can help too.
Instead of use templates you can generate a RDF representation of the spreadsheets and easily transform the RDF data into YARRRML, RML or R2RML. This can be done manually reading the data and generating the graph with rdflib or you can create a mapping for the "csv" files (each sheet of the spreadsheets) and generate the rdf with tools like RDFizer or RMLmapper. I can help too.