The ornamental design for a broadcastcontrolbox, as shown and described.
FIG. 1 is a front view of a broadcast control box, showing our new design;
FIG. 2 is a rear view thereof;
FIG. 3 is a left-side view thereof;
FIG. 4 is a right-side view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof;
FIG. 7 is a front-right perspective view thereof; and,
FIG. 8 is a rear-right perspective view thereof.
The broken lines in FIGS. 3-5, 7, and 8 depict portions of the broadcast control box that are not part of the claimed design. Any shading and cross-hatching are not features of the design but are utilized to illustrate the surface contours of the broadcast control box.