If you are using FileMaker 11 or 12 you can define a portal filter for this, and let me know if you want to know how to do that, but I'm going to suggest an "old school" approach that exploits using a global field set up with a checkbox set to filter values at the relationship level as I think that it's simpler to set up:
Say you have this relationship for your portal to show both te "yes" and "no" related records:
LayoutTableOccurrence::PrimaryKey = PortaltableOccurrence::ForeignKey
Define a global text field, gSelectYesNo in The data source table for the layout's table occurrence.
Modify your relationship to be:
LayoutTableOccurrence::PrimaryKey = PortaltableOccurrence::ForeignKey AND
LayoutTableOccurrence::gSelectYesNo = PortalTableOccurrence::checkSwitchField
Place gSelectYesNo on your layout and format it with check boxes for Yes and No.
If you click the Yes, check box, you'll se all related records with "yes" in the checkSwitchField. If you click "no" you'll see the records marked "no" and clicking both check boxes will show records with either value.
A lazy man would use two tabs, Yes and No combined with the filter idea above. The Yes tab would filter for Yes and the No tab filter for No. Since the portal layout can be the same hardly any effort at all.
Filter Tab Yes = Field = Yes
Filter Tab No = Field = No
This may be too easy for some people to accept... :)
Thanks Jack, this is an option that had not occurred to me and it is indeed simple to implement, though with it you can't see both lists at once as you can with the checkbox field based relationship--suppose you can add a third tab with no filter labeled "Both" for that...
Hi Jack and Phil
thanks for your input, I will have a play.