Is it possible to label/export the 'total' from the Invoice package?

The invoice package helpfully uses calc to add up the total amount owed. Is it possible to label this total and then reference it elsewhere in the document? This would be quite useful as obviously the total amount due is helpful to put in a covering letter. In the example below, I would like a way for X to be mytotal or some other variable, where mytotal produces the total from the bottom of the table in the invoice.

documentclass{article}
usepackage{invoice}

begin{document}
    Dear Sir,
    Please find below an invoice for EUR X.  Please pay within 14 days.
    Yours,
    Donald Knuth

    begin{invoice}{Euro}{19}
    ProjectTitle{Sales Restructuring}%
       Fee{Sales Structure Analysis}   {2750.00}   { 6}
       Fee{Negotiation with Agents}    {2750.00}   { 3}
end{invoice}


end{document}