I use this to make it readonly using WSH:

IF FILE("C:\scanned2903.tif") THEN
oFSO = CREATEOBJECT("Scripting.FileSystemObject")
oFile = oFSO.GetFile("C:\scanned2903.tif")
* Set the read-only bit.
oFile.Attributes = BITOR(oFile.Attributes, 1)
ENDIF
######################################
I use BITOR to make it read only.
I don't know how to reverse the BITOR.

Thank you..