If you mean you are doing English to Greek translation, there are several tools that will help.
The Hopperizer Perseus lookup tool (http://www.katabiblon.com/tools/perseus-hopperizer/index.php
will let you do both English to Greek dictionary searches and also Greek to English ones.
Unicorn, a word processor program (http://www.quasillum.com/software/unicorn.htm
for Ancient Greek and Latin, has dictionaries and spellcheckers for both languages. It also does Hebrew. It is a Java-based program and will work on Macintosh OS X, Windows, and Linux systems.
Kalós is a Classical Greek verb conjugator, dictionary, and morphology tool. It has both Windows and Mac versions. Get it at http://www.kalos-software.com/
Hope this helps,