samba - Apr 2007 - accessing samba shares from a winpc sometimes as a readonly user and sometimes with writing abilities

hello everyone.
i am trying to setup samba and there is a whole lot of option in doing
things.. so i got somewhat overloaded:)
the idea is that i want in my home network to setup a file server running
samba (its a slackware v11 machine)
and have all my music/video/office files on the server..

now, from a windows side i know that when u log onto a pc you will probably
be asked to input  a passwd. it also gives you the option
to 'save' that logon username and password so that you will not have to
enter it everytime you try to log onto the shares..
what i was thinking and hoping to implement is a slightly more dynamic
system, where for normal activity , ie listening to some music
watching a video or smth i logon as a user that has no write priviledges...
and if i want to save some files or to modify , i log on as a different
user..
but windows do not give you the option to change this password once you have
asked of them to 'remember' it.

is there some way tha samba offers to persistently ask for a password when
someone tries to save in a read only folder.
is there some alternatively that does not work exactly like that but might
work in similar manner?

thank you in advance for your help
nass