Exit a subroutine

I am trying to convert an old Star Trek game that I made with SDLBasic.

I have a piece of code that RC just doesn't like...



sub AWA()
Canvas(3)

' send an away team to mine the planet
if shields <> 0 then
prints("")
prints(" You must lower your shields before the shuttle craft can depart.")
wait(3000)
else
if nplanetsector = 0 then
prints("")
prints(" But Captian, there are no planets in the quadrant.")
wait(3000)
else
for i = 0 to nplanetsector-1
if abs(planetx[i]-esx)<=1 and abs(planety[i]-esy)<=1 then
e = rand(planete[i])
prints("")
prints(" The away team has successfully mined " + str$(e) + " units of Dilithium.")
prints(" You are being re-fueled and re-armed.")
wait(3000)
energy = energy + e
planete[i] = 0
stardate = stardate + 0.5
exit sub '<<<<<<<<<<<<<<<<<<<<<<<<<
end if
next
prints(" But Captian, we are not adjacent to a star with a planet.")
wait(3000)
end if
end if
end sub


"ERROR:Expected {DO | FOR | WHILE} in EXIT statement"

Is there a "work-a-round" that can solve this problem?

Any assistance would be appreciated. But, do not spend too much time on this issue, it's not a priority. Just seeing "If I can..."  lol