Depends what checkbox you are using
From the "forms" toolbar one..
Right click - format control - control tab and choose a cell to "link" (i.e B1)
From the "Control" toolbar
Right click - properties - and type "B1" into "linked Cell"
This will make True or False in the Cell
Then in A1 type
=--B1
Which will turn the True/False to 1 or 0