Calculate Time Difference If With Multiple Criteria

I'm trying to calculate the difference in time between two times if certain criteria are met.
I want to calculate the time difference between a DP Activity Status by Tom Smith and the most recent prior CF or RC activity status by anyone other than Tom Smith on the same order.

Results would look something like this…
4 Columns of data (A:D) – Formula in 5th column (E)
A---------------B-------------------C--------------D---------------------E
Order #-------Activity Status----Worked By----Time-----------------Time to DP
80001234----AC------------------Mike Fox------1/2/14 7:53am----
80001234----ER------------------Mike Fox-------1/2/14 9:02am----
80001234----RP------------------Mike Fox-------1/2/14 9:15am----
80001234----CF------------------Mike Fox-------1/2/14 10:30am----
80001234----DP------------------Tom Smith----1/2/14 12:30pm----2:00
80001234----AC------------------Brain Jones----1/2/14 2:21pm----
80001234----RC------------------Brian Jones----1/2/14 2:54pm----
80001234----DP------------------Tom Smith----1/2/14 3:35pm------0:41
80001235----RC------------------Lisa Bond------1/5/14 9:17am----
80001235----DP------------------Allen Miller----1/5/14 10:01am----
80001235----RC------------------Jerry Monk----1/5/14 10:15am----
80001235----DP------------------Tom Smith----1/5/14 10:20am----0:05
80001235----CF------------------Mike Fox-------1/5/14 12:05pm----
80001235----DP------------------Allen Miller----1/5/14 12:30pm----

I did it with:

E3:

=IF(A3&B3="DPTOM",C3-LOOKUP(2,1/(($A$2:A2="CF")+($A$2:A2="RC"))*($B$2:B2<>"TOM"),$C$2:C2),"")

But you'll need to insert spaces between the times and the meridiem. And I'd recommend changing your post title, so that it's more search engine friendly and less screamy.

Thanks for your help! I can't seem to get your formula to work.