Read/Write using DS and RENAME

I'm trying to Combine two files with the same record format name.  I was 
trying to use LIKEREC and Datastructures to do this.  I'm on V5R2.  I'm 
getting "Data Structure MREC is not allowed for tis operation" at compile 
time.  Here's some snips of the code...

     FCUSTOMR   IF   E           K DISK    Rename(GXCUSTOMR:FHTCUST)
     F                                     Prefix('F')

      // MSA customer master by customer name
     FMSCSTL1   UF A E           K DISK    Rename(GXCUSTOMR:MSACUST)
     F                                     Prefix('M')


      // Record Definitions
     D FRec            DS                  LIKEREC(FHTCUST)
     D MRec            DS                  LIKEREC(MSACUST)



      /Free

        READ FHTCUST FRec;

        DOW NOT %EOF(CUSTOMR);

            // Add Customer
            MREC = FRec;

            WRITE MSACUST MREC;

            READ FHTCUST;
        Enddo;


       *INLR = *On;

      /End-Free


I get this error on the "WRITE MSACUST MREC;" line.  I thought that you 
could just specify a DS on the write command.

thanks!

Jeff Stevens
Mize, Houser & Co. P.A.
913 451 1882
JStevens@xxxxxxxxxxxxxx