Defining a Valid if

[Jennifer_Matsun]

@Steve Kindly assist me with the following.

I have table a read only look up table

Select Project Name (A) >> Phase (Platform) >> Stand Number (10)

Data will be captured in table Form

Select Project Name (A) again >> Phase (Platform) again >> Stand number ( Only 20 and 30) should show because 10 is already selected.

Select Same Project Name (A) >.> Different phase (Roofing) >> Stand number that should show is (10,20, 30) . I want stand numbers to show from 10,20,30 because its a different phase selected .