I used the command /ti. You will get an error for invalid command and I don't think that can be stopped. But here it is:
on 1:input:*:{ if ($left($1,3) == /ti) {
timer [ $+ [ $right($1,$calc($len($1)-3)) ] ] $2-
}
}
To change the command change the 3 in:
on 1:input:*:{ if ($left($1,3) == /ti) {AND
timer [ $+ [ $right($1,$calc($len($1)-3)) ] ] $2-to how many characters the command is (including the slash).
Also change the /ti in:
on 1:input:*:{ if ($left($1,3) == /ti) {to the command.