Input of cst

No you cannot setoff input of CST againts liability of CST, the logic behind it is that cst is the revenue of the state if you setoff input cst which is the revenue of other state againts revenue of your state it will be loss to your state.

Eg: If you purchase some goods from say state A then it will be revenue of state A. and then you sale some goods in your state or outside your state it will be revenue to your state.against which you can setoff intrastate purchases which is also revenue to your state, but if you setoff purchase from state A it will be loss to your state thats why it is not allowed.

You can refer Indirect Tax Book from the Author Sanjay Bangar.

Yes I agree with Gaurav....mjk