You need to create a batch file.
open notepad and simply type
del C:\Documents and Settings\<USER NAME>\Local Settings\Temporary Internet Files\*.* /q
save this as "ANYFILENAME.bat" (without quotes) anywhere you like. Then create a shortcut to it where you want it, open the properties of the shortcut and set the shortcut key. you should be able to use ctrl-f or ctrl-alt-f but probably not just f (seeing as how you'd run it every time you typed a word with f in it!).
Also make sure that path is correct, it is on my machine, but you never know.
let me know if it doesn't work, either reply here or PM