When I got more serious into my brewing water I found a water calculator from Kaiser before I found Ez Water and Bru'n Water. I have it on my netbook but I do not remember where I found it. I guess I came across it maybe from a Google search. But anyway, he has a colum for blending waters to come up with a combined water profile.
I took a screen shot but I don't know anyway to get into my post. If interested pm me, I guess I could email it. If you are just looking for calculations I'm no help there.