Try this..
http://ucsc.cmb.ac.lk/ltrl/services/feconverter/t1.html
and then click on the 'Show Transliteration Scheme' button to see key-combinations for each Sinhala letter.
Hope this will resolve ur matter.:)
yakadooo... mu meka copy karan awith thiyenne www.thelastrow.com eken neda... REP illana eka nam waradi man hithanne.. adu gane reference wath dapanko... CREDIT GOES TO THE ORIGINAL AUTHOR!! :(