SKIPREC only skips a specified number of records (e.g. skip first 5 records). It cannot skip groups of records. You can use the technique shown in the "Include or omit groups of records" Smart DFSORT Trick at:
If you need more specific help, you need to give a better example of your input records (with more than one group) and expected output records, and explain clearly the "rules" you want to use to determine which groups should be skipped. Also, give the RECFM and LRECL of the input file.