Need Imacros expert to help with pasting into a browse form

I've wrote an Imacros script for posting and need to enter in a file name on this page http://beatcaptchas.com/captcha.php the problem is that you can not paste into the filename box. I need Imacros to paste in the location of my file such as C:\myfile.txt. Can someone tell me how to do this please? If I have Imacros click the Browse button it wants to save a file not choose one an upload it. Need some help on this one. Thanks.