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How do you create a conditional value list? Answer ID: 5833Last Updated: Sep 29, 2011
FileMaker Conditional Value List Example VIDEO
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There are two methods you can use to do this. One is "dynamic" it will always display the current values from the related record. The other is "static", it copies the current values from the related record in to corresponding fields in your current layout's record. Both methods can be useful in different situations so you will need to evaluate the needs of your project and choose.
Here's a thread that describes both methods: Auto Fill