Supplier Invoice - Calculate Total Amounts via Webservice

Hello,

I'm creating a supplier invoice via webservice.

I have an operational problem: the invoice is created with net amounts and uses the taxation codes existing inside bydesign.

When the document is created the Total Gross Amount isn't determined automatically, and I would prefer to avoid calculating the total gross amount for the service call, as I do not have the percentage of taxation corresponding to the tax codes available.

Is there a way in the service call itself to tell bydesign to calculate the total gross amount, or is a call to "calculategrossamount" inside the before-save the only possible way?