In worksheet 1, column A I have a long list (350K rows) of dates and times
of an event (namely when an ambulance goes enroute to the hospital..)

In worksheet 2 (8K rows) I have data from hospitals with times they are
unable to accept ambulances with column A (start date/time) and column B
(stop date/time)

My goal is this: In a new column (column B, worksheet 1) I need a formula
that creates a flag for every transport in worksheet 1 that occurs during any
time between Columns A and B in worksheet 2.

I can use "if" statements to analyse one row but I can't figure out how to
compare multiple rows...I'm using Excel 2007 for windows.

thanks