Need to show when volunteers are available
I am making a db for a festival. We have several concerts and lots of volunteers. I have created a layout where I can fill in all the information about each concert.
I have a portal where I can choose (from a valuelist in the first portal field) the volunteers from the "volunteers" table and the result is stored in a joining table ("WorkConcert") between "volunteers" and "concert". This works fine. But I would like to be able to filter out the volunteers that are not available on the date of the concert. I now have a available field on the volunteers table with a checkbox field based on the concert dates. I have tried Portal filtering using PatternCount ( Concert::Date ; Volunteers::Available ) but this only works if a vlounteer is only avialble one day. And the volunteers still show up in the valuelist but won't show in the portal if they are unavailable, very confusing and obviously not the way to do it.
The perfect solution (i think) would be if the valuelist it self only showed the volunteers actually available on the concert date.
Second question is there a way to avoid that a volunteer can be selected twice in the portal?
I really appreciate all help, thank you!