The ornamental design for a icon for a computerscreen, as shown and described.
FIG. 1 is a front perspective view of an icon for a computer screen
comprising the present invention, the broken line drawing of a computer
screen is for illustrative purposes only and forms no part of the claimed
design; and,
FIG. 2 is a front view thereof, on an enlarged scale, the broken line
drawing of a computer screen if for illustrative purposes only and forms
no part of the claimed design.