Magento - Minimum Order Amount Based On Category

We use Magento as our e-commerce package and currently have a module called Fooman Surcharge to enforce a global minimum order surcharge at the cart. Currently this means that any orders under £15 have a fixed fee of £7.00 added to them. What we want is to set a separate minimum order fee for a specific category (perhaps this could be defined by a special attribute). This would result in any orders from category X, that are under £40, have a surcharge added to them to make up the difference. e.g a product costing £10 has £30 added and so on. We would like to keep our current global minimum order fee in place. Extra information: - Magento version 1.4.2.0 Thank you.