How do I calculate change from baseline based on multiple measurements from a single subject?

[#1]

I have data collected at baseline (t = 0) and after various different treatments for a number of subjects. What is the best way to calculate a change from baseline without copying and pasting baseline data for each participant? As an example, I have data for different participants with different treatments that are collected daily. I'm struggling to figure out how to automatically return the baseline column data (shown in blue font) below so that I can calculate a change from the baseline. Any ideas on how to do this? 

Subject	Treatment	Day	Endpoint measurement	Endpoint Baseline (mean)	Endpoint change from baseline
M1	Baseline	1	53	54	-1
M1	Baseline	2	55	54	1
M1	Tx1	3	70	54	16
M1	Tx1	4	72	54	18
M1	Tx2	5	32	54	-22
M1	Tx2	6	35	54	-19
M2	Baseline	1	50	52.5	-2.5
M2	Baseline	2	55	52.5	2.5
M2	Tx1	3	100	52.5	47.5
M2	Tx1	4	90	52.5	37.5

[#2]

Your question got stuck in the spam filter, not sure why.

[#3 · Accepted solution]

The formula for the Endpoint Baseline (mean) column is:

Col Mean( If( :Treatment == "Baseline", :Endpoint measurement, . ), :Subject )

The formula for the Endpoint change from baseline is

:Endpoint measurement - :"Endpoint Baseline (mean)"n