Just thinking out loud for the moment. You should be able to create an expression that is true no matter what the value on the constant is.
So my test case is a Multi-selected field " Dependency Downstream Impacted Projects" based on projects. My condition is
( Dependency Downstream Impacted Projects = 'AACE Test Project' or Dependency Downstream Impacted Projects != 'AACE Test Project' )
( mvLookup( mhs_depend.mhs_ds_imp_proj, "SCH_BROWSE_PROJECT", 5117157, "EQUALS" ) ) || ( mvLookup( mhs_depend.mhs_ds_imp_proj, "SCH_BROWSE_PROJECT", 5117157, "NOT_EQUALS" ) )
In the constant I just pick the first project is equal or is not equal so when this value changes to any value the start condition should be true.
Just thoughts,
Gene