Any validity checking program gurus here?

I'm experimenting with a validity checking program on a command.

It works just fine from a command line. But if I try it in a CL program, within SEU, then SEU immediately crashes, and I get this:

'*JOBD' may not be qualified if specifed for job queue.

(which is the message I'm sending from the validity checking program), and then this:

Receiver value too small to hold result.
Dump output directed to spooled file 1.
Error found on STRSEU command.

The CL source for the validity checking program is more-or-less straight out of the manual:

PGM PARM(&MINHEAP &MAXHEAP &JOBQ)
DCL VAR(&MINHEAP) TYPE(*DEC) LEN(4 0)
DCL VAR(&MAXHEAP) TYPE(*DEC) LEN(4 0)
DCL VAR(&JOBQ) TYPE(*CHAR) LEN(20)
IF COND((%SST(&JOBQ 1 10) *EQ '*JOBD') *AND +
(%SST(&JOBQ 11 10) *NE ' ')) +
THEN(DO)
SNDPGMMSG MSGID(CPD0006) MSGF(QCPFMSG) +
MSGDTA('0000''*JOBD'' may not be +
qualified if specifed for job queue.') +
MSGTYPE(*DIAG)
SNDPGMMSG MSGID(CPF0002) MSGF(QCPFMSG) MSGTYPE(*ESCAPE)
ENDDO
IF COND((%SST(&JOBQ 1 10) *NE '*JOBD') *AND +
(%SST(&JOBQ 11 10) *EQ ' ')) +
THEN(DO)
SNDPGMMSG MSGID(CPD0006) MSGF(QCPFMSG) MSGDTA('0000Job +
queue name must be qualified with either +
a library name or ''*LIBL''') MSGTYPE(*DIAG)
SNDPGMMSG MSGID(CPF0002) MSGF(QCPFMSG) MSGTYPE(*ESCAPE)
ENDDO
ENDPGM

--
JHHL