Mailmerge Switches

How would I do an IF statement where IF a check box is null then do
nothing but if yes, then enter a field.

This is what I am trying to do - { IF {MERGEFIELD FT Contract} = TRUE
(or "") then insert {MERGEFIELD "Start"} otherwise enter text "N/
A"} " }

This is the formula I am using but can't get it to work.

{ IF "{MERGEFIELD FT Contract}" = TRUE "{MERGEFIELD Start}" {"N/A"}
" }

I am thinking it is something like this but it does not work.
Any help would be greatly appreciated.
Thanks in advance.

Debbie