Distribute pay across associates for packages

We offer several packages to our patients which we have to invoice in full at the first visit (e.g. 680€ for a package with 12 visits, full invoice of 680€ issued after 1st visit). This leads to the fact that all visits no. 2-12 are invoiced as 0€. As our associates have a variable pay based on their generated turnover, this can lead to problems. E.g. associate 1 does visit no.1 and gets allocated the full 680€ in turnover, associates 2 does visits no.2-12 but does not get paid for it. Is there any way you can develop a feature to deal with such cases?