You can if your mouse has the functionality to do what you want.
Computer Mouse, Wireless Mouse, Bluetooth Mouse | Microsoft Hardware
This application looks pretty nifty though: http://www.magictoolbox.com/magiczoomplus/
Hold the Ctrl key and use the mouse wheel.
If you haven't found the help you need, here are some 'work-arounds' using the Magnifier and your system settings:
To Magnify Entire Page: Start, Search pane, and type: magnifier. When it comes up click the plus (+) sign. The entire page will magnify. OR go to: Control Panel, All Control Panel Items, Ease of Access Center, Make Your Computer Easier to Use, Start Magnifier.
16. Magnifier – To Magnify a Certain Portion of the Screen - go to Start, Search pane, and type: magnifier. Click the program at the top. The Magnifier can be set to Docked Mode which places a re-sizable window at the top of the screen that follows the cursor. (To read more about Magnifier go to Start, click "Help & Support" on the right hand side, type in "magnifier.") Magnifier is actually located at: Start, All Programs, Accessories, Ease of Access, Magnifier.
There is only one which works for Win7 with one key and mouse:
Hold the Cntrl key and scroll mouse.

@Dwarf @rroad thanks mates, now I try your tip and report how it comes up![]()

to change the shortcut keys for magnifier search for it in start menu ,when it appears then right click it and select properties. and enter the keys of your choice in the shortcut window.although it will make it ctrl and alt then the key of choice by default.
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i wouldnt change them though as you lose the shortcut keys to close it ,ie win and -.
also when the magnifier is open and in lens mode then pressing the win key and + zooms it, keep pressing + for more zoom
like i said i wouldnt change it ,
out of interest why do you want to change it.