Renaming 'unassigned' slice

[Susan Papp]

Hallo Everyone,

Solaris  9

I recently had opprtunity to reformat a disk and  wanted to change
'unassigned' tag slice 3 to be /opt

3 unassigned    wm     957 - 1156      460.16MB    (200/0/0)    942400

System does not allow it, saying /opt is 'not expected'

Enter partition id tag[unassigned]: opt
`opt' not expected.

QUESTION
Disk is not mounted.  Am thinking slice tag can only be assigned as 'opt' @
installation time. More likely I am  doing something wrong. Anyone know how to
assign the tag?

Thanks

Sue