Great tip!

One change is needed in my opinion though:

Should be "(%ERRLEV1% | %ERRLEV2%) & 24"

(untested)

Otherwise you'll miss error code(s) in cases when e.g.

ERRLEV1=8 and ERRLEV2=16

or

ERRLEV1=24 and ERRLEV2=0

Edit:

Hope this example illustrates my point:

select (8 & 16) & 24 as errorcode_lost

select (8 | 16) & 24 as errorcode_active

select (0 | 16) & 24 as errorcode_active

select (8 | 8) & 24 as errorcode_active

select (5 | 6) & 24 as no_errorcode

select (0 | 0) & 24 as no_errorcode