Actually, this is something that your mouse driver is doing for you. (Mr Peabody, set the wayback machine for 1997, so that we can see what happened when wheel mice were introduced...)

When wheel mice were first introduced, there really weren't any application that supported the mouse wheel. MS Office and Internet Explorer did, and that was about it. In every other application you could roll the mouse wheel all you wanted and nothing would happen. So, in order to increase sales, mouse manufacturers added code in the mouse driver that converted wheel messages into scroll messages, thereby implementing scrolling support even for applications that didn't use the mouse wheel.

Fast forward a few years, and most applications are wheel aware, including PSP. Most of them just use the wheel to scroll, so everything is peachy.  But some, including PSP of course, use the mouse wheel for zooming, so if the mouse driver translates wheel messages into scroll messages you get the app behaving differently depending on whether it has scroll bars or not.  This is double plus ungood.

*Most* current mouse drivers have the ability to mark certain applications as having native mouse wheel support, thereby disabling the translation that the mouse driver implements.  How do you tell the mouse that PSP uses the wheel and to leave the futzing thing alone?  Unfortunately that varies by mouse vendor, but in every case you should start by going to the control panel and double clicking on the mouse applet.  Usually somewhere in there you can find someplace where you can enter a list of applications that directly support the mouse wheel.   -Joe Fromm

Intellimouse, open the driver in the control panel, click the wheel tab> and then > advanced > then add PSP to the list of apps not to use the mouse wheel support. -Ron

I had been using an Intellimouse, but have switched to a Logitech cordless using the MS drivers. Joe's advice seems to have fixed this.  I disabled wheel support via the mouse applet for PSP.  -Maxxed

Mouse wheels are ultra-friendly with the Tool Options & many other PSP dialogs.  Nearly everywhere we find dials, levers or numeral entry fields --> we have the ability to "wheel roll shop" through all those settings.  Roll wheels to fine-tune numerals one increment at a time; to custom fit brushes; and to spend more productive time on your images and less time in those palettes & dialogs. 

Most fields respond to a single click to activate, however several (generally associated with scroll lists) require the double click. Double clicking will always work on everything.  It may be easier to initially just double-click everybody, until your wheel shopping/clicking habits are committed to memory.  The natural progression of usage eventually shows us which guys honestly require double clicks versus those other guys (the majority) who will activate on a single click.

Finding an easy way to develop your "mouse wheel shopper habit" is the only goal.  Use any click method, that suits your style.

• Enable auto  proof
• Mouse-click any lever to make it active
• Return to your image
• Roll your wheel & watch shadows move on the image as you redirect them with your wheel without physically resetting the numbers on your dialog box.  As long as you don't click that mouse anywhere in your PSP workspace, you can continue to wheel roll your settings up and down for viewing & shopping.
  
  
• Activate your Drop Shadow dialog's Blur lever (not shown) to roll-enter those decimal settings.  We can instantly preview 20-30-40 different blur settings by simply rolling our wheel and watching our previews update & change on that image.   No need to return to the dialog box to enter new or different numbers.