MESSAGE concatenation......!

Hi Experts,

I am displaying message like "Document XXXXXXXX posted successfully:. Using standard message class .

<FS_FCAT>-SCRTEXT_M   = 'Message Class'.

   <FS_FCAT>-COLDDICTXT  = 'M'.

   <FS_FCAT>-FIELDNAME   = 'ID'.

Now i would like to add 'INTERNAL' before my message id . Just Like " Internal Document XXXXXXXX posted successfully".

So how can ii concatenate it to message.

Thanks,

Suresh