Best Formula for mid year schedule changes

[CMaroney]

Hello - new user, but long time lurker of all the great info here.

I'm trying to come up with a formula that will show when an employee start time should be.

REPORT BACKGROUND:

Some employees switched start times during the year and in conducting a review of actual start times vs scheduled start times, and I need to be comparing the proper start for the given day

I have a table that shows:
Name | date start time changed | start time
Fred 8:00
Bill 8:30
Bill 3/1/2011 8:00
Mary 8:30
Susan 8:00
Susan 4/1/2011 8:30

Fred has always been 8:00
Bill was 8:30 then on 3/1/2011 changed to 8:00
...

On a data sheet, I have the employee name and the time the employee logged in.

On a summary tab, I have a dropdown to select the employee, then the following columns
date - start time - actual log in time - difference between start and login.

(The calculation shows out of office, on time, or how many actual minutes late)

I want to be able to have a formula look at the name, then date and find the appropriate start time.

I'm not married to any table or formula - so if there's a better way to structure the start time table, I'm open.

Thanks in advance for your time!

C