relating to the "latest" children

[bcooney]

I'm not sure where to post this question. I have three files; patients, lab dates, testresults. Each patient can have many lab dates which can in turn have many tests. They are related this way:

Patients

_kP_Patient ID

Lab Dates

_kP_LabDateID

_kF_PatientID

TestResults

_kP_TestResultID

_kF_LabDateID

I want "see" from Patients the last set of test results, that is, the testresults that would have the greatest labdateID for that patient and capture them in a value list. If I create in patients a calc field MaxLabDate = max (patients::LabDateID), I can't use this in a relationship bcs it doesn't index.

I remember back in FM5 days a technique that used the max function to "see" the latest set of records. Can't recall how it was done. I can't find any custom functions that seem to do the trick. Any ideas?