automation envelopes for delay

Hi guys, newbie here,
I'm trying to insert an automation envelope for delay. So that I can have the delay at selected parts of the track only. 
Reading the online help instructions, I click on the Edit Filter control, select Automation, select Delay, and always wind up with a long list of delay parameters that I can control via envelopes. BUT not an option for delay itself.  Aaargh !  What am I doing wrong ? I just want to turn the delay on and off, not any of its parameters. 
thanks much,

Actually, I would think using a send is really the best option. Even if the delay has an "off" toggle parameter, it would likely cut off the delay echo and sound awful.
 
Create a new stereo bus, put your delay on that, then in your source track, add a send that points to the new bus. Use automation on the source track's send volume to control what gets sent to the delay.
 
Regards,
Dan

Ok guys, good stuff.  I've tried it both ways...  using both the MIXL and MIXR parameters in Sonitux FX delay (can't afford a nice delay plug-in right now), creating an automation envelope for both. (Have to apply envelopes to both for it to be and on/off type thing). BUT...  somehow things get confused and the dry signal is delayed as well.  Don't know what the deal is there, but this method doesn't appear to work for that reason.
But... creating the "new buss" method does work.  There are volume level issues that have to be sorted out (master goes into clipping readily), but it does work. I guess same would apply when I want to add modulation in a different part of the track... create a new bus just for modulation effects. 
You guys are great...  take the rest of the day off !

+1 to automating the send level. That's the best way to do it. Don't try to automate the mix control, you don't want any dry signal from the delay bus.

Sometimes this selective delay thing works well, sometimes it doesn't. You're likely to get better results if the part is quantized MIDI, otherwise it's very hard to position the automation nodes exactly in time with the notes you're sending to the delay (so you might lose part of the notes, especially the attack).

Sometimes I'll give up trying to automate it and just add an identical instance of the synth I'm working with, pan it appropriately and manually program the delay as a whole new part. You have 100% flexibility this way and can be a lot more creative.

Don't forget you can add delay to individual clips. I do this all the time for something like a snare drum "splash." The only caution is the delay stops when the clip stops, so sometimes you need to extend the clip duration.