A value from field based on another field in a related record...
I'm having a complete brain-timeout and know this is easy but can't remember how to do it. The set up is that I have a main table linked to a related table with routes that relate to a starting point selected in the main table. The possible routes that can be taken populate a value list. The user picks from one route from that list (via radio buttons). In the table the routes have numeric IDs (Sensor_Id). I need to create another field in the main table to return the ID based on the route selected.
Related records appear value list:M8N-Hwy 80N and Main
M8S-Hwy 80S and Main
M5N-Hwy 5N and Main
M5S-Hwy 5S and Main
User Selects: M8N-Hwy 80N and Main
(in that record in the Routes Table there is a field Sensor_Id that has the value 123456)
I need another field used in a web portal expression in the main table to return 123456.
Any help would be appreciated. I have forgotten how to make this happen.