This can be done using WebEasy's "group" function.
Solution
1) Put two images on your page.
2) Make them exactly the same size and position:
- select them both (hold down CTRL and click each in turn)
- right-click one of them and select "Fit -> Make Same Size"
- right-click one of them and select "Fit -> Make Same Position"
3) Select both images. You can do this by dragging a selection rectangle around them.
4) Right-click on the selected images and select "Group"
5) Go to the "Build" menu and select "Preview".
6) Click the "Options" button.
7) Check the "Dynamic HTML" box.
8) Click OK.
9) Click OK again to preview your site.
When you roll your mouse over the images that are the same size and position, they will change.