VMS Help DTM, CREATE, COLLECTION, Command Qualifiers, /VARIABLE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

   /VARIABLE=(variable-name=variable-value,...)

   Overrides the values of the specified global variables for
   this collection. If you override the value for more than one
   variable, separate the variables with commas and enclose the
   list in parentheses. If you override only one variable, omit the
   parentheses.