How to Include Tax in order-detail.tpl

[WZ810]

I would like to replace the products (incl. tax) with just the tax on line 90.

                   {l s='Tax:'} {displayWtPriceWithCurrency price=$order->getTotalProductsWithTaxes() currency=$currency convert=0}

I thought it would be a simple

price=$order->getTotalProductsWithTaxes()

MINUS

price=$order->getTotalProductsWithoutTaxes()

but I can't get the code to work.

Does anyone know how to accomplish this?