Rather than a channel that has a "fixed" value (numeric or string), this new "calculation channel" type would be a function of other channels.  Currently, if Channel3 = Channel1 + Channel2, and then I change the values for either Channel1 or Channel2, I have to re-execute the calculation
 
ChnCalculate("Ch(""Channel3"") = Ch(""Channel1"") + Ch(""Channel2"")")
 
Now, if there was a "calculation channel" where I could define Channel 3 as "Channel1 + Channel2", I wouldn't need to perform this re-execution! 
 
Another way to explain is to have a channel that works like Excel calculation cells.  The cell calculation stays the same, and when the input cells change, the result cell is automatically updated. 
 
I'm not sure if I explained this well, please ask for clarification if necessary.