I have data as below :
  DISTNAME    DLIBSEQN    LIB_DEVT    GLIBSEQN    GRID 
                                                       
  ????????    ????????    xxxxxxx                     
  yyyyyyyy    B2797       3584-L22                     
  zzzzzzzz    10000       GRID                         
              1001A                    10000           
              1001A                    10000           
              1001A                    10000           
              10015                    10000           
              10015                    10000 
So based on the DLIBSEQN variable value if it match with GLIBSEQN variable value for all observation it should update the GRID value with the name of the DISTNNAME found from first record where we have zzzzzz ....