Interactive map, zoom in and out problems, a little more advanced over claudio's ver

I have developed a map, and having much difficulty. I have created the overall windows like platform for viewing the map etc. But In terms of the map interactivity I am having problems.

My aim is to have a zoom function, which looking at claudios is similar, but this is simply a zoom in and out, what I was after was in increments of say : 50% view to start off, then 100%, 150%, 200%, 250% and so on, on click of a plus button. The minus would simple revert in the same increment form.

Also the ability to drag the map, obvoiusly using the startdrag and stop drag functionality.

Can anyone help me achieve this, any direction help would be ideal at this point as I am all out of answers.

T