Accessing a field in the parent form

Accessing a field in the parent form

I am trying to build a deluge script in a sub-form field (on user input) but I need to use a value from a field in the parent form.  I thought they were linked together but I did not see the list of fields in the criteria section, so I tried the following: (Form_name.Field_name), but that didn't work.
 
Example: I have a field "Gender" in a customer form (parent), but the detailed sub-form is where I perform calculation based on the gender of that customer.
 
Can you see/access the parent fields from the sub-form?
 
Any help would be appreciated