How to send a uniqueidentifier as a parameter ?

[Yovav]

I want to add a uniqueidentifier parameter to a store procedure,

so I added it to the store procedure:
@ShowBlock uniqueidentifier

and on the ASP page:
oCmd.Parameters.Append oCmd.CreateParameter("@ShowBlock", adGUID, adParamInput)
oCmd("@ShowBlock") = CAST("{35D78965-D84E-4891-8310-3C280B66099F}" AS uniqueidentifier)

but I'm getting an error:
Microsoft VBScript compilation (0x800A03EE)
Expected ')'
/Gallery/Admin_Categories.asp, line 109, column 67
oCmd("@ShowBlock") = CAST("{35D78965-D84E-4891-8310-3C280B66099F}" AS uniqueidentifier)

How should I do it ?