to use QKeySequence or an alternative to it

I have a current need that I need to be able to construct key sequences as and when a key is pressed (that includes the modifier). Currently QKeySequence does not handle my requirement but am using it such that its being constructed everytime a key is pressed or released. Also another thing that I noticed is that when only the modifiers are pressed (which is a valid case in my requirement), I should be able to generate a valid QKeySequence, however it does not until there is a non-modifier key (anything other than Ctrl/Shift/Alt/Meta).
Also it would be ideal to say have QKeySequence::addKey(key) [that will add a key to the current sequence] and QKeySequence::removeKey(key) [that would remove an existing key from the key sequence] to extend it.

It would be great if anyone could let me know to get this work with QKeySequence or an alternative.

-
Thanks.