I wanna build a Client/server application, in Local Network for office about 30 clients.
Here is the scenario (for now only 3 clients for example):
There are 3 computer clients having their own data ,say :
ClientA – has data A.xlsx,
ClientB – has data B.xlsx,
ClientC – has data C.xlsx),
and those data A,B,C have relationship to any other.

And also I want to add some enhancement to the application-excel such :

ENHANCEMENT 1 – data update automation
When Client A is updating its own data (data A.xlsx),
the data B.xlsx and dataC.xlsx are automatically updated .
When Client B is updating its own data (dataB.xlsx),
the data A.xlsx and dataC.xlsx are automatically updated .
also when Client C is updating its own data (dataC.xlsx),
the data A.xlsx and dataB.xlsx are automatically updated.

ENHANCEMENT2 – data permissioning
Client A are allowed to WRITE dataA.xlsx, but READ-ONLY (and querying is also allowed)to dataB.xlsx and dataC.xlsx
ClientB are allowed to WRITE dataB.xlsx, but READ-ONLY (and querying is also allowed)to dataA.xlsx and dataC.xlsx
Client C are allowed to WRITE dataC.xlsx, but READ-ONLY (and querying is also allowed)to dataA.xlsx and dataB.xlsx



QUESTION :
1. I want to use EXCEL as the database storage. (is it possible ? ) – I hope it’s possible – if not, the solution please.
2. What is the best programming language for such case ? (considering the reliability, scalability, high performance). Many people give an advice to use PHP for such case, any advice ?
3. Any other advice or comment ?

Full thanks . . . .