Hi all this is tediously basic i assume, sorry. A line chart shows all items that are in "Geography_Type A" where the user can choose the Type:

 

And what i need to do is have a second "Geography_TypeX" (which happens to contain a single geography) because that is in effect our target, or average, or main comparator, the orange line sketched in here:

 

But how?  the table structure is like this

Date        Geography    Geography_Type        value

various    various            A,X, whatever               

 

Sorry if this isn't clear! thanks, Adam