|Excel Developer Reference|
Returns or sets the degree of transparency of the specified fill as a value from 0.0 (opaque) through 1.0 (clear). Read/write Double.
expression A variable that represents a LineFormat object.
The value of this property affects the appearance of solid-colored fills and lines only; it has no effect on the appearance of patterned lines or patterned, gradient, picture, or textured fills.