The ornamental design for a cupholder for slidableinteraction with a hollowarmrest, as shown and described.
FIG. 1 is a perspective view of a cupholder for slidable interaction with a hollow armrest showing my new design, and shown in association with a hollow armrest depicted in phantom outline, and not a part of this invention;
FIG. 2 is a top view thereof;
FIG. 3 is a side view thereof, the unshown opposite side being of identical appearance;
FIG. 4 is a bottom view thereof; and,
FIG. 5 is an end view thereof taken from the left of FIG. 2.