Something

/m {
if ($1) {
   if ($1 = 1800) {
   /mode #lurk +m
   msg #lurk $me has set the channel on +m for 30 minutes; Reason: $2-
   .timer 1 1800 /mode #lurk -m
   }
   if ($1 = 3600) {
   /mode #lurk +m
   msg #lurk $me has set the channel on +m for 1 hour; Reason: $2-
   .timer 1 3600 /mode #lurk -m
   }
   if ($1 = 7200) {
   /mode #lurk +m
   msg #lurk $me has set the channel on +m for 2 hours; Reason: $2-
   .timer 1 7200 /mode #lurk -m
   }
   else {
   /mode #lurk +m
   msg #lurk $me has set the channel on +m for $1 seconds; Reason: $2-
   .timer 1 $1 /mode #lurk -m
   }
}
else {
   /mode #lurk +m
   msg #lurk $me has set the channel on +m for 10 minutes.
   .timer 1 600 /mode #lurk -m
}
}