From Xojo Documentation
Formats the contents of the control when it loses the focus.
It uses the same formatting conventions as the Format function. To turn off formatting, set the Format property to the empty string, "".
If you need to enforce an entry format rather than permitting any entry, use the Format property in conjunction with the Mask property. See the description of the ValidationMask property and the section "Masks" in the Notes section.
This line applies a dollar format when the user tabs out of the field.