State Management :: Updating The Viewstate Object Before Saving It To The Database?

I have overridden the following methods:

LoadPageStateFromPersistenceMedium()
SavePageStateToPersistenceMedium(object viewState)

in a class that my page derives from, so that the viewstate can be stored in DB.

Now, on page_load of my page, I am checking what control caused a postback & based on that I am forcing execution of 2 button click events in a row (by overloading those click events & calling them explicitely), but the behaviour I want is as if the execution of those 2 button click events went through the regular page life cycle.

Here is the sequence of events that happen in typical page life cycle & notice I want to alter behaviour at step 4 (on load):

1) Initialization

2) LoadViewStateData (here the viewstate is loaded from my database using the overridden LoadPageStateFromPersistenceMedium)

3) LoadPostBackData

4) Load

Here, I would like to force execution of 2 button_click events based on whether a particular control posted back.

4.1) imgBtnPrev5_Click()
4.2) imgBtnPrev4_Click()

Now, when the imgBtnPrev5_Click() is executed, the viewstate is already loaded, so we are fine. But after execution of imgBtnPrev5_Click(), I would like to update the viewstate object in memory & then call the overridden SavePageStateToPersistenceMedium (by passing that updated viewstate object as its parameter) and then before execution of imgBtnPrev4_Click(), I would like to call the overridden LoadPageStateFromPersistenceMedium.

5) RaisePostBackEvent

6) SaveViewState

7) Render

My question is, how do I update the "viewstate" object of the page - that is passed to SavePageStateToPersistenceMedium with the changes made to the controls in imgBtnPrev5_Click()?