Many developers will be familiar with the formatting of columns on a datawindow. You will also know that there are two toolbar icons for the currency and percentage formats. You can add your own formats to the toolbar and as a result change multiple columns to the same format.
Here's how to to do it.

1. Customize the toolbar by either using the Toolbar option from the windows menu followed by customize or by using the right button menu Customize.
2. Select Custom items to add to your toolbar
3. Drag an icon to the desired location on the toolbar.
4. Select the format button and either pick a format or enter a new one and give it some help text.