The below query gives you the list of storedprocedures and the text contained in it.
I am not sure if you will be able to update the syscomments table. I haven't tried it. I thought this could be of some help to start with.
select so.name, sc.text from syscomments sc inner join sysobjects so on sc.id = so.id
where so.xtype = 'P' and sc.text like '%TEXT SEARCHING FOR%'
Thanks,
Manjari.