Matching and Comparing data from sheet1 to sheet2

[appreciateyourhelp]

Hello there,
sorry if this has been asked before - I don't know the lingo yet ; )
I would like to match 3 to 4 columns of data in a row in sheet 1 to the same data and amount of columns in Sheet 2 a
ie matching between Project ID & Activity Id & Activity Name
and find differences in one or two the columns ie: % completed and Activity Status

What I trying to find is when data has been updated (not when it remains the same) can I highlight the changed in the data in current week ?
I was thinking to make it easy to update each week I could insert new data into the same columns in Sheet 1 (last weeks data) and Sheet 2 (this weeks data) each week and keep the formula in sheet 3 ?

I have found when I concatenate I sometimes get a problem when a user has added extra spaces after a word or number or when the dash changes from a short dash to a long dash, problems like that are stopping me from matching in concatenation correctly and I have thousands of rows to check so want to make it easy and successful
I really appreciate your reading this and helping if you can - thank you Helen ; )

for example :

Sheet 1 (last weeks data)
Project ID (column 1 title)

Project ID	Activity ID	Activity Name	Start	Finish	% Complete	Activity Status
ABC-234-65	MOB-123	activity name 1	12-Jan-17 A	12-Jan-17 A	1	COMPLETED
ABC-234-65	DRP-123	activity name 2	15/05/2017	19/05/2017	0	NOT_STARTED
ABC-234-66	DRP-2032	activity name 3	04-Apr-17 A	30/06/2017	0.3001	IN_PROGRESS
ABC-234-66	DRP-2033	activity name 4	04-Apr-17 A	30/06/2017	0.3001	IN_PROGRESS

<tbody>
</tbody><colgroup><col><col><col><col span="2"><col><col></colgroup>

Sheet 2 (this weeks data)

Project ID	Activity ID	Activity Name	Start	Finish	% Complete	Activity Status
ABC-234-65	MOB- 123	activity name 1	12-Jan-17 A	12-Jan-17 A	1	COMPLETED
ABC-234-65	DRP-123	activity name 2	42870	42874	0	NOT_STARTED
ABC-234-66	DRP-2032	activity name 3	04-Apr-17 A	42916	0.3001	IN_PROGRESS
ABC-234-66	DRP-2033	activity name 4	04-Apr-17 A	42916	0.3001	IN_PROGRESS

<tbody>
</tbody><colgroup><col><col><col><col span="2"><col><col></colgroup>

 

[appreciateyourhelp]

sorry meant to make these changes
Imagine I have changed in Sheet 2
under % complete from 30 % to 45% and Activity Status changes from In-progress to completed