Importing external bookmark (.dat) files into many MXDs using arcpy?

Does anyone know any python script to use for arcview to import a bookmark (saved as a .dat) that was created and saved externally using ArcMap?
I tried with this script but without a result:

import arcpy
from arcpy import env

env.workspace = r"F:ProjectsRoniabaloa"
for mxdname in arcpy.ListFiles("*.mxd"):
    print mxdname
    mxd = arcpy.mapping.MapDocument(r"F:ProjectsRoniabaloa\" + mxdname)
    df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0]
    arcpy.LoadSettings("F:ProjectsRoniabaloagislayersb1.dat")
    for bkmk in arcpy.mapping.ListBookmarks(mxd, 'Bookmark1', df):
        df.extent = bkmk.extent
 mxd.save()
 del mxd  

I’ve also searched all documentation and forums with no luck.