umxGxEbiv with 2 moderators

I'm interested in the moderation effect of an interaction between two moderators on a phenotype of interest. umxGxEbiv is fantastic for one moderator, but does not accept two moderators, even though the Purcell model allows it. Is there a way to use umcGxEbiv with two moderators (and thus estimating their interaction effect as well)?

Thanks!