The vertical bar is only needed at the front if you need to have multiple separated items within a single variable expanded to multiple items in the list, which is not the case here.
Just use:
%CkBoxVarName%|0|1
The first time you run it, it will be a popup menu - select 0 or 1 and to set the initial value of CkBoxVarName and after that it will be a checkbox.
This is because:
0|0|1 is a checkbox defaulting to 0 (same as 0|1)
and
1|0|1 is a checkbox defaulting to 1 (same as 1|0)