Simple on text Run Time For Seconds, Minutes, and Hours. Make Sure You Have Online Timer On You Can Turn It On By Clicking The Timer Button On Your mIRC Toolbar and Checking The Online Timer Checkbox. If You Don't Have Online Timer On This Script Will Not Work.

on *:TEXT:!Run:#: {
  Set %r $online
  if (%r > 3600) { Goto Hours }
  if (%r > 60) { Goto Mins }
  if (%r < 60) { Goto Seconds }
  :Seconds
  Notice $nick $me Has Been Running For %r Seconds
  Goto End
  :Mins {
    Set %r $round($calc(%r / 60),2) minutes
    Notice $nick $me Has Been Running For %r
    Goto End
  }
  :Hours {
    Set %p $calc(%r / 60) 
    Set %p $round($calc(%p / 60),2) hours
    Notice $nick $me Has Been Running For %p
    Goto End
  }
  :End
  Unset %r
  Unset %p
}