Are you able to provide a bit more information and context on what you are trying to achieve? Are you referring to deployment tasks created from software packages in Software Distribution? If so, perhaps something like the following session relevance might work:
(name of it, values of mime fields whose (name of it = "x-fixlet-swdCommandOverride") of it) of bes fixlets whose (exists mime field "x-fixlet-swdCommandOverride" of it)
