To check if a yes/no field control is ‘true’ or ‘false’, use this build-in system function:
if ( fld('Field_yn').isTrue() ) { Your code here; }
This will return ‘true‘ if Field_yn is true (and false if Field_yn is false).
if ( fld('Field_yn').isFalse() ) { Your code here; }
This will return ‘true‘ if Field_yn is false (and false if Field_yn is true).
NOTE: You must get the capitalisation correct, i.e. lower “i” and upper “T” or “F”.