Find duplicates and compare month started versus finished

[FROGGER24]

In colum j would like the results of looking in column "D" to find duplicate transport name, then look in columns Q & R to see if the month is the same for all of the duplicates find in column d. If the months are the same leave cell blank, if months are different then the move ,
"crossed over"

For example one transport can carry 6 parcels and if any of the 6 started in one month and finished in the following month then that entire parcel would be considered a crossover move.