Dear All,
in case anyone else needs CASIR volume 3, I finally managed to find it on DLI, catalogued as "four reports made durning the years 1862-65 vol.3"

The DLI link is:
http://dli.gov.in/cgi-bin/metainfo.cgi?&title1=four%20reports%20made%20durning%20the%20years%201862-65%20vol.3&author1=cunningham,%20alexander&subject1=india,%20antiquities&year=2000%20&language1=english&p ages=287&barcode=99999990842309&author2=&identifier1=&publisher1=&contributor1=&vendor1=NONE&scanningcentre1=ignca&slocation1=NONE&sourcelib1=central%20archaeological%20library,%20%20asi&scannerno1=&digitalrepublisher1=&digitalpublicationdate1=0000-00-00&numberedpages1=&unnumberedpages1=&rights1=OUT_OF_COPYRIGHT&copyrightowner1=&copyrightexpirydate1=&format1=tagged%20image%20file%20format%20&url=/data51/upload/0022/884

Have a nice day,
Daniel