Fields are enterable unless you set them through field behavior to disallow entry in browse mode. Fields can also have conditional format attached so that they change their formatting depending upon the conditional format calculation. But fields remain fields. Maybe if you explained a bit more, we could figure out what you want to do.
it is simple:
2 tables a,b a is connected to b with a default foreign key - key relation. If I create a button with conditional formatting: b::key = true and place this button in the body section than the b::key field is shown in table view as an open, editable field, which is obviously something I don't want.
I dont know what your button has to do with conditional formatting (http://www.filemaker.com/products/fmp/conditional_formatting.html) but if you do not want your related ID field to show, then delete it from the layout. If you want to show it but do not want users to enter it, then as LaRetta pointed out already, change the field behavior to where they can not enter the field.
If I create a button... and place this button in the body section ... in table view...
No button works or can stay into the body part in Table View.