Each record in the table must have a unique combination of certain fields

[HansBades]

I want to make the combination of three fields only in the record to be unique. 1 out of the three fields can be different from the others but all three cannot be the same in each record. I need each record in this table to have a unique combination of these three fields. How would I do that? I tried the index feature but it didn't work. Thanks.

[June7]

Setting compound index should do that. Why didn't it work - what happens?

If you want to provide db for analysis, follow instructions at bottom of my post.

[ranman256]

Make a key field ,
run an update query to combine the 3 fields.
key the field,
save.

[June7]

Save data dependent on other data? Should not be necessary.

[CJ_London]

I tried the index feature but it didn't work.

If 'didn't work' means it wouldn't allow you to create it, it will because you already have data that breaks the requirement - review your data and correct as necessary
It should look like this

[HansBades]

Thank you all. I got it working now. Really appreciate the advice.