Excel 2007 : vlookup returning an array of values

I have an array of records with one value that repeats:
Key_1 Val_a
Key_2 Val_b
Key_1 Val_c
Key_3 Val_d
Key_2 Val_e
Key_1 Val_f
Key_1 Val_g

On a different sheet I would like to find and output all records that have Key_1.
This can be easily done with macros and I am interested about how to do that using standard excel functions.


Thank you!
A