is it possible to make some keyword in a template and then when it loads to ce it replaces itself with some other text?

i want to have some keyword lik [#date], [#username] and when it loads or before it loads to ce i want to replace these words with the actual value. something like System Messages  in sitesetting in dotnetnuke 2.1.2.

 

if it is not possible do you have any sugesstion on how to do this?

thnx