Cool - your registration is linked now.

What you suggest above won't work correctly - that will add up the number of hands where you called to the number of hands where you checked, which isn't what you want.
Firstly, there is a built-in stat for check/calling as preflop aggressor. This is "Call F Float Bet", and there are turn and river versions too.
If you also want a general check/call stat regardless of preflop action, read on.
What you need to do here is to create a new pair of columns to count the number of times that you check/called, and the number of opportunities you had to check/call.
I assume that in this case an "opportunity" would be when you check and face a bet or raise.
There are a couple of different ways to build these columns, but this is how I'd do it.
cnt_f_check_call =
sum(if[lookup_actions_f.action LIKE 'XC%', 1, 0])
cnt_f_check_call_opp =
sum(if[lookup_actions_f.action LIKE 'X_%', 1, 0])
Then you can make a new stat with this expression:
(cnt_f_check_call / cnt_f_check_call_opp) * 100
You can duplicate each of these and change the _f_ (flop) to _t_ for turn and _r_ for river.