Find Missing Data From Table

what is the fasted way to get all the rows from table1 that aren't in table2? i have over 4000 rows in table1, i am currently looping through using:

for each dr as datarow in dt1.rows
then i check table2 to see if that entry exists using:
dim rows() as datarow = dt2.select("EmployeID = " & dr!EmployeeID)
if rows.length > 0 then it exists in both tables - dont need it

other wise i copy the row into a third table which ends up being my final collection of rows that are in table1 and not in table2. this takes a really long time. is there a better, faster way that isn't too complicated?