Hi,
To get a modal like appearance, use a cell with a static that can be overlayed. Then in javascript when a person clicks link / button to cause a "child" like window for data entry to open, adjust the size and location of the cell and static control to completely cover the entire browser page and then turn on the visibility to it and another cell that holds the fields to enter.
To see this in action, check out schedule sample that ships with WebDev.
Cheers!
Ken