Just draw a black box over the old box.

DECLARE SUB popup (x AS INTEGER, y AS INTEGER, colour AS INTEGER)
SCREEN 12
TYPE regtype
ax AS INTEGER
bx AS INTEGER
cx AS INTEGER
dx AS INTEGER
END TYPE
DIM regs AS regtype
regs.ax = 0
CALL interrupt(&H33, regs, regs)

DO
regs.ax = 3
CALL interrupt(&H33, regs, regs)
CALL popup(regs.cx, regs.dx, 3)
t! = TIMER
WHILE t! = TIMER
IF INKEY$ = CHR$(27) THEN SYSTEM
WEND
LOOP

SUB popup (x AS INTEGER, y AS INTEGER, colour AS INTEGER)
STATIC oldx AS INTEGER, oldy AS INTEGER, phase AS INTEGER
IF x < oldx OR y <> oldy THEN LINE (oldx - 32, oldy - 14)-(oldx + 27, oldy + 11), 0, BF
COLOR 7

CLS

LINE (x - 30, y - 150)-(x - 30, y - 250)
LINE (x - 230, y - 150)-(x - 230, y - 250)
LINE (x - 230, y - 150)-(x - 30, y - 150)
LINE (x - 230, y - 250)-(x - 30, y - 250)
oldx = x: oldy = y
END SUB


'P.S. the word is helicopter.