Looking for Ideas and a solution.
I have a table with four columns. Lets call them ColA, ColB, ColC and
ColR.

(The table represents finding a tyre code from a manufacturer).
Suppose A has three different values in it 13, 15, and 17.
For each of these values B has several values such as 145, 155, 165
etc perhaps up to ten different values for each value in col A.
Col C has several values for each value of B. Col R is the 'result'
that we are trying to find.
So a few records from the table could look like:

13,145,45,P
13,145,50,Q
13,145,65,R
15,155,50,Q
15,155,60,R
15,155,75,T etc

The user needs to enter a lgitimate value for A then one for B then
one for C and hence get the result from R.

So I have the table called 'tyres' and i put a query on col A
select distinct A from tyres,

Then another query on col B
select distinct B from tyres where A = :A

Then another query on col C
select C,R from tyres where A = :A and B=:B

Passing the values from one query to the next. Fine it works.
But why not Master-Detail. OK I set that up, that works nicely.

But these are actually lookup combos and I want to link them into a
table called Cars.

As soon as I try to make a query operate in Master-detail and link
its keylink to the Cars key it all siezes up solid.

For example query B says 'select distinct colB from tyres'
master source is a source from queryA
master links say colA=tyres.colA
keysource is source from cars query
keylinks say colB (of course cars has a colB).

I have struggled for two days. But I get a message on the lines
of 'multiple lines from a singleton query'. As well as assorted key
violations.

Perhaps I am approaching the problem from the wrong end.

Any ideas welcome.