Programming help - how to get the read-only state of PDF file is windows explorer preview is ON?

Programming help - how to get the read-only state of PDF file is windows explorer preview is ON?

I'm developing an application where a file is need to be saved as pdf. But, if there is already a pdf file with same name in the specified directory, I wish to overwrite it. And in the overwrite case, read-only files should not be overwritten. If the duplicate(old) file is opened in windows (Win7) explorer preview, it is write protected. So, it should not be overwritten. I tried to get the '

FILE_ATTRIBUTE_READONLY' using MS API 'GetFileAttributes', but it didn't succeed. How Adobe marks the file as read-only for preview? Do I need to check some other attribute of the file?

Thanks!