I wouldn't say it's about Fields vs. Variables... The problem, as I see it, is because the field PCR can hold multiple values, separated by comma. If you could separate the values in your load script, it would be the best. You can use function subfield() to do it.
If you can't, the only compromise I can see is to always link to the first value, using the same function subfield():
Another compromise - you could also have a variable where the user would decide what element to link to , and replace "1" with the variable? Not very elegant, but does the job...