Field Names in File Field

I have a file that holds the field names from multiple files. I was 
wanting to use these field names to control what is going into a flat 
file. So that if one was delete from file or added to file it would 
control what fields went into flat file.


File holding values has three fields    X , Y , and Z. with X and Y as 
Keys and Z holding my field name from other files
Example Z=CUST with CUST being field name from other file.

I get all fields populated with values from their files.   CUST = 123

If  I do an EVAL OUTFILE = OUTFILE + %TRIM(Z) + X'05' + etc.

Will my value of %TRIM(Z) be CUST or 123. For some reason I think CUST.

And if so has anyone done something like this or have examples. 

My mind is blank and 
I have no way to test on iSeries right now.

Thanks 
Bill H

Any thoughts, comments, or thumps on the Head excepted?!....