Code:
if portb.7 = 1 then
USBBuffer[0] = 0
USBBuffer[1] = 0
USBBuffer[2] = $33 ; 33 = ";"
USBBuffer[3] = 0
USBBuffer[4] = 0
USBBuffer[5] = 0
USBBuffer[6] = 0
USBBuffer[7] = 0
ELSE
....clear buffer...
ENDIF