Problem using Lookup inside Sumifs

Hello,

The following example shows a simple worksheet and a Sumifs formula used to calculate the total net price based on 2 conditions...

Example1.png

However I don't want to have to bring in the Size column as this data is already in another sheet. What I would like to do is something like the following where the size is looked up from another range...

Example2.png

However the Lookup within the Sumifs doesn't work. I thought it would as it acts on its own like a range. Any help would be appreciated, thanks.