I have file which is repeating, and i want to insert a row after the end of each repitition.

here is my sample data from:

123 sat
123 sat
444 mat
444 mat
444 mat
555 abi

to:
123 sat
123 sat
new row insert
444 mat
444 mat
444 mat
new row insert
555 abi

I know it involves a macro and i dont know how. pls help as its a HUGE data and i need to automate it.

many many thanks
tesfamichael