Zend certified PHP/Magento developer

Magento 1.9 – Sales Rules – subtotal with TAX

I want to add to sales rules for cart a rule where to add subtotal with TAX because I cannot relay on subtotal without TAX as I have products with different TAX class and different VAT values.

For example I have a product with VAT 19% and a product with VAT 9%, the I cannot trust the subtotal without TAX value, as it will depend on what type of products I add to the cart, in order for the rule to work correctly.

I want to apply a rule for subtotal bigger than 200 but I need to have subtotal with TAX.

How can I do this?