Solved: Sharing Permissions

hi every one

I have a problem with sharing permission's.The actually problem I kept a folder in sharing in which there are different files.some times what happens is two different users access one file at a time without knowing and save the data from were the real problem creates.i need to give permission like if one user is accesing the file the other user shuld get read only until he uses.

thx in advance

 

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bump

 

we dont get much in this forum.I googled and solved the problem.