Having problems with Midi Session Drummer

Hello everyone and thank you for taking your time to read this. Let me get right to it.
 
I have recently switched over from Reason to Sonar x3 and am in the process of learning how to use Session Drummer 3. I have watched many videos on how to use Session Drummer 3 and in particular, midi sequencing with SD. Everything is going well except I can't quite get a handle on how the midi sequencing works.
 
Basically, I am just trying to figure out how to make drum pattern fills using the SD3 midi sequencer. I have not been able to find a good example of this in the videos that I have seen. I don't think that I have found one video yet that uses x3.
 
What is making me crazy is that when I try to double click in the drum track lane, as I have seen others do in videos to edit an SD3 midi part, it (the double clicking), does NOT bring up the midi sequencer part that I need to edit. Instead, it simply remains as it was from the original, first pattern that I made and can't be altered.
 
What I have been doing so far is:
 
A) make a pattern
 
B) drag pattern out for however long I want it
 
C) Attempt to create a fill by holding control and dragging a part over to where I need the fill. At this point, I do the double clicking in the Session Drummer track lane (on top of the midi data). The idea is to use this dragged over part of the pattern to write over to create the drum fill.
 
This is where I am having the problem primarily. Sometimes this method works okay but most of the time I am unable to write over the top of  the other pattern because it  (don't know what exactly) won't let me write over it, nothing happens at all except a bell sound. Other times, after I do the double click, I see an empty midi sequencer box that is ready to be written into.
 
I realize that this is confusing sounding but I don't know how else to explain this. I am hoping that some of the more experienced Session Drummer 3 users will understand what I talking about here.
 
If someone would be so kind as to make a quick guide (like what I did up above) to show how they did these tasks I think I could finally get this figured out. I can make patterns and even the fills but can't reliably go back and edit. Its like I have to get all my patterns and fills perfect the first time or face having to redo everything from square one if I make a mistake. Surely, this is not Sonar's way-is it?
 
By the way, I have downloaded the Master Class videos on this but the guy in the video, who uses x1, uses something called "Layers" to accomplish the pattern changes and fills. I don't think that I have this on x3 or do I?
 
Thanks for reading and I will appreciate any info on this problem that you have. If I need to clear anything up please let me know.
 
Thanks
 
bob