Hspice - create cell variants for process variation

Hi all, I am running into an interesting problem with Hspice. I am trying to simulate variants of a cell ( with varying tox in my case) using the same spice netlist. I do not want to use the .alter statement. What I want to do instead is somehow redefine the PFET device model parameter toxp for different instances of the PFET device. Multiple parameter defintions dont work, the last defn is used for commands even before that appears. One option I tried was .option parhier local, which allows local scoping of parameters. This works for length, width but does not seem to work for tox ( which is a sort of pure model parameter). Is that fundamentally an issue with how model parameters are used in hspice simulation, or is there an elegant workaround to .alter ( one which will obv save some cpu time). Any suggestions will be appreciated. Vineeth