Delphi simple function

I need to create this function function Addtext (target_filename, text:string) : boolean; The target_filename wil be a BINARY file, and the text must be added in the begin or that file. Example : if Addtext('c:\[login to view URL]','hello world') then... The function will open the target file, insert the text at the BOF (begin of file) and save it again. Send small demo.. please , and I will award.