ERROR: could not find rrdtool. Use PathAdd: in mrtg.cfg to help mrtg find rrdtoo

[.::afisb::. .....]

hi ,
i install mrtg-2.12.1 on RedHat systemand run it.my mrtg is working properly 
and
creating .png, .log and .html files but when i add PathAdd in c.cfg file it 
gives this error message:
"ERROR: could not find rrdtool. Use PathAdd: in mrtg.cfg to help mrtg find 
rrdtool"

My c.cfg file includes:

EnableIPv6: no
WorkDir: /var/www/html/cihaz1
Options[_]: bits,growright
LogFormat: rrdtool
PathAdd: /home/zehra/rrdbuild/rrdtool-1.2.9/bindings/perl-shared   //RRDs.pm 
file is in "/home/zehra/rrdbuild/rrdtool-1.2.9/bindings/perl-shared" 
directory so I wrote it with PathAdd.
I wait  your answers please help quickly!!!!!!!!!!!!!!!