You didn't say you were trying to spam this message to 200 channels.
In mirc-options/irc/flood do you have the boxes checked to "enable flood protection" and "own messages"?
Other than that, if you want to show a message every 100 milliseconds:
//timerxyz -m $chan(0) 100 msg $!chan( $!calc(1+ $!timer(xyz).reps ) ) test message
You can save yourself a lot of trouble by putting your message into a %variable and having the timer reference only the alias:
/set %VariableName Test Message
//timerxyz -m $chan(0) 100 CustomAlias
alias CustomAlias {
var %i $calc(1+$timer(xyz).reps)
msg $chan( %i ) %VariableName
}
