My best bet would be to first READ the file, capture the contents in a variable (for example MyContent). Then manipulate the variable MyContent, and write the manipulated file to the filesystem. Sounds complicated, but check out the following code:
<cfset TheFile="C:\inetpub\
<cfset TextToAdd="Hello World!">
<cfset BR="#Chr(13)#"&"#Chr(10)#">
<cffile action="READ"
file="#TheFile#"
variable="MyContent">
<cfset MyNewContent="#TextToAdd#"&"#BR#"&"#MyContent#">
<cffile action="WRITE"
file="#TheFile#"
output="#MyNewContent#"
addnewline="Yes">
Beautiful isn't it? ;-)
<webguru>iqof188</webguru>