one way to handle this would be to use a flag, set the flag to zero at the start of each loop, then after the user has clicked, check if they have clicked somewhere valid (ie in one of the boxes and also if the box is empty) and if so set the flag to one, then at the end of the loop check if the flag doesnt equla zero, and in either case do what it has to do, either loop again until it is set or jumpo to the pat of ya code for the next player
eg: (btw this is psuedocode)
startofloop:
do
flag=0
`game code
if valid_area_clicked then flag=1
`check what to do next based on flag value
if flag=1 then gosub next_player_stuff
else
loop
ok thats not proper code but should give ya the idea, i dont have time to write the code on how to do this at this time
cheers
optic blast! megablast! have a blast!!