I am sorry Kevin if my last picture gives you a wrong image, the grey zone is the sub-form with the fields: credit coll and value.
The Main Form has Credit #1 and Credit #2 as fields.
Main Form is linked to Main Table
Sub Form is linked to Table A
So, in Table A, I have only one column (Credit Coll) with the collection of Credit numbers (Credit #1 and Credit #2) and the corresponding values.
In Main Table I have 2 columns of Credit numbers, Credit #1 and Credit #2, without values, only numbers which can be found in Table A in Column Credit Coll.
The exampe I gave was to show you that if in the Main Table a "e" is shown (from Credit #1 - Main Table), I should see a value in the subform of "4,565" as result.
So, I assume that the field "Credit Coll" has to be linked to Credit #1 and Credit #2 in the Main Form (child - parent).
If I link only the Credit #1 with the Credit Coll, the right result will show on the value, the same thing will happen if only Credit #2 is linked to Credit Coll, it will work. But if I link Credit #1 and Credit #2 with Credit Coll the same time, it doesn't work ... it doesn't output any values in the "value" field in the subform.