I need vb help

Okay I know that you can go like for example if i put in this code

Dim aa as string
aa = "dxlglthj"
aa = right(aa , 3)


then you would only see dxl, but i want it to do something like were it read from char number one to like 3, like for example i know this is not really a proper vb6.0 code but i want it to do something like this

Dim aa as string
aa = "tfrhkruyg"
aa = (aa, 3-5)

and then the result would be like "hk, so the string aa would now contain hk instead of "tfrhkruyg"

Thanks people,sorry, just if you dont no can you post not if you do and you dont wanna tell me, bravo for you, you can mock me.