problem in dynamic filtering of sharepoint data ??

Question

I have a SharePoint list with two columns

cat1 cat2
A     AB,AD,AE
B     ABC
C     AB,AD
D     ABC
E     AB

I m querying list using CAML and displaying Cat1 with the help of repeater like this as a navigation panel for my page:

A
B
C
D
E

When I am clicking on A(it will produce query string ?Cat1=A) it will show on the right hand side webpart AB,AD,AE

and on the left hand side it will make B and D disable(thats the main problem) and I am only able to click A,C and E if I will click on C(QS:?Cat1=A&Cat1=C) it will show on the right hand side (AB,AD) If I will click on E(QS:?Cat1=A&Cat1=C&Cat1=E)) it will show on the right hand side AB

So basically I m trying to do filtering through it.I am not worried about how rite hand side data is coming as It is through query string and it can be filtered easily based on that.But the problem is how to filter left navigation panel .

As shown above B and D got disabled so how to make this thing dynamically posible? Any idea what should be the best approach to get started ...