Enforce single use of a record in a relationship

np,
A Parent can have many children, but a child may only have 1 parent.

ie a Sample if the sample is setup as a Child in a relationship, it may only be attached to one parent as a child. 

So the only Samples that are available to use are where there is no parent.  I like to set up a field on the Parent called [Parent Exists?] as a formula checkbox field with a formula of true and look that up down to the Child.  Just in case the parent gets deleted, and yet [Related Parent] sill has value in it but the child is now once again an Orphan.

Thank you for the response!

That makes sense but where I am struggling with that is how do have my list of Samples without having a Parent to relate them to? Doesn't it require a Parent to create a child record?

It does not require a parent existing to create a child.
Consider the invoicing and time tracking system for a non so theoretical QSP (QuickBase Solution Provider) like myself.

I log my time (Add time records) and these are time records that will later need to be attached to a parent invoice.  Then at the end of the month I push a button to mass update them to attach them to the correct parent invoice that will not be created until I sit down to do my monthly invoicing.  So the children get created all during the month and the parent only gets created at the end of the month.

I think Yearend has fried my brain, so apologize for the constant clarifications.
Of course, you are correct the child is not required to have a parent.
I have played around with a couple of different ways.

If I do a Two Table setup I don't see how to select existing data into the parent. 

• Is it just manually creating a blank parent and then going to a report on the child table that filters out any with an existing parent and adding the new parent ID?
• Is there a way to do that directly from the parent?  

Using 3 tables it appears to work by using a filtered report in the join to filter out any that have existing parents just cannot do it from grid edit.

Thank you again for your help!

I am going to go I think simpler on this but let's see if I get the basics.
1 main sample to be combined with another of 4 samples. The 4 samples are limited so they can only be used once and I assume the main sample is a quantity of 4 since you want to combine it with 4 other samples (separately of course).

I would make a text formula to combine the sample names [Main Sample]&[Limited Sample] then mark the field as 'must be unique' which will prevent the combination to be duplicated. (give a real mean warning...okay not that mean).
Then put the limited sample in a table and the main samples in another table. Even if I am wrong about the main sample you can use this method to prevent combinations.

Thank you both!

It is actually combining 5 different samples to create a new single sample.
Each of the 5 samples has specific characteristics(data) and we are wanting to combine the 5 to create a unique new sample with a new set of characteristics. Some will be measured and some will be through calculations based on data associated with each of the 5 samples used.

Now some new information as I discussed the suggestions with the project manager this evening was that they want us to be able to use the newly created samples in future combinations as one of the 5 samples used to create a new combination. Same rules apply that once a unique sample is used in a combination it can no longer be used in any future combinations. All samples, including those created through the combination, have a unique 8 digit text serial #.

This is getting outside the scope of what I was asking in the initial question and I need to re-evaluate the app.

If you have any further thoughts I am always grateful for any advice/help.
Either way, Thank you both for your time and thoughts!

No problem. I like puzzles. Once you are sure what you want there is definitely a way to improve the workflow using a some native, (no script) but somewhat advanced techniques with URL formula buttons.

You mentioned you need to re-evaluate but I wanted to mention the possibility of a "slotting" system. If you can figure out a way to categorize the sample data into 4 or 5 unique parent tables, then each slot will contain data unique from the others. For example, Slot 1 contains samples 1 through 10, Slot 2 contains samples 11-20, etc.. 

You can take this further by creating form rules that display messages if slot1 =slot2 (parent 1 = parent 2) etc. Or you can create a formula field that generates a unique number that is required in order to save the record, but the number is only generated when no slots are matching.