How to avoid using multiple variable definitions in each metric

Hi ,

below is my metric formula,

(sum(tch_assign_succ{node=~"^$node"})/(sum(tch_assign_att{node=~"^$node"})-sum(tch_assign_no_tch{node=~"^$node"}))
)*100

Node is my label which I have defined as a variable to filter my reports, Issue is I have long formulas which consist of 20 + metric query sum, to filter this i have to put {node=~"^$node"} the pattern for every metric that adding to this formula

is there a way to avoid this … see one of the examples is below