MoveFileEx

or maybe:

If GetAttr("C:\Myfile.txt") And vbReadOnly Then
    SetAttr "C:\Myfile.txt", vbNormal
End If

Because:
MOVEFILE_DELAY_UNTIL_REBOOT      
Windows NT only: The function does not move the file until the operating system is restarted. The system moves the file immediately after AUTOCHK is executed, but before creating any paging files. Consequently, this parameter enables the function to delete paging files from previous startups.

How can I replace OrigionalFile under thses conditions?
====================================

how can temporary make the orginal file writable( remove read only flag) using  filesystemobject
and then set it back to read only.

But if for security reasons (permissions) that is not possible then consider copying the file to another file
and then use the copy of the file (which is not read only)