You can increase a global variable in a timer, then check if 2 is (not) a multiple of the value of the variable to see whether it should send response 1 or 2:
//set %myvar | .timerrmsg 0 300 inc $(%myvar |,) msg #chan/nick $($iif(2 \\ %myvar,response 1,response 2),)
Of course change #chan/nick to the recipient of the message, and response 1/2 to your liking
