The ornamental design for a penholder for a cellular phone, as shown and described.
FIG. 1 is a perspective view of the pen holder for a cellular phone, the
phone depicted by means of broken lines being shown for illustrative
purposes only and forming no part of the claimed design;
FIG. 2 is a front elevational view of the pen holder for a cellular phone;
and,
FIG. 3 is a side elevational view of the pen holder for a cellular phone.