The ornamental design for a portion of an electronicmouse, as shown and described.
FIG. 1 is a front perspective view of a portion of an electronic mouse showing our new design; and,
FIG. 2 is a top view thereof.
The broken line showing the remainder of a portion of an electronic mouse is for illustrative purposes only and forms no part of the claimed design. The lines radiating out from the u-shaped region of a portion of an electronic mouse are used herein to represent illumination of the u-shaped region.