sql server 2008 / replacement in a field / from position /with specified width / with specified substring

is there any function in sql server 2008 that do the belo开发者_如何学运维w job :

i want to replace in a field / from specified position /with specified width / with a specified substring...

how can i do that ?

thanks for helping me

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Have you looked at the STUFF function? It appears to meet your requirements.