The ornamental design for a topsheet for a sanitarytowel, as shown and described.
FIG. 1 is a view of a topsheet for a sanitary towel showing my new design, wherein the area between the two parallel broken lines illustrates the environment in which the article embodying the claimed design is used and forms no part of the claimed design; and,
FIG. 2 is an enlargement of the encircled area 2 of the top view of a topsheet for a sanitary towel shown in FIG. 1.
The broken line showing of two parallel lines down the center, as well as the border around the design, depict portions of the topsheet for a sanitary towel that form no part of the claimed design.