Flash 8.
fill.overflow
Property; a string that specifies the behavior of a gradient’s overflow. Acceptable values are "extend", "repeat", and "reflect"; the strings are not case-sensitive. The default value is "extend".
The following example specifies that the behavior of the overflow for the current selection should be "extend":
var fill = fl.getDocumentDOM().getCustomFill();
fill.overflow = "extend";
fl.getDocumentDOM().setCustomFill(fill);