Help - how to pass a "keyed parameter list" to a macro or function - beginner is at wits end

How can I pass a keyed argument list to a function  ? to a macro?

For example:

(setf  aspec '(:a 1 :b 2 :c 3))

(defclass obj () (a b c))

(make-instance 'obj aspec)    <<<<<

 >>>   Malformed plist in doplist, odd number of elements.

Clearly aspec is being evaluated before the call to make-instance

so I have been trying something like:

(defmacro create-obj (arg)
    `(make-instance 'obj ,@arg))

This does not expance correctly, and I have tried everything under the 
sun that I could think of , except the correct method?

Any suggestions?

Thanks,

David Koch
[email protected]