Macro to add attachment in compose window

[mimosinnet]

Hi all,

I have a macro in the compose window that adds an attachment to the 
mail:

macro compose U "<attach-file>/home/mimosinnet/.mutt/signatures/signature_uab.html<enter>"

Would it be possible to get the macro executed when entering the compose 
window, without pressing the key? 

My company wants this signature in the e-mails :(

Thanks!

-- 
Mimosinnet
Linux User: #463211
41:25:16N (41.421110) 2:11:28E (2.188333)