multival = arcpy.GetParameterAsText(1)  # 'Store_1;Store_2;Store_3'
vals = multival.split(";")

where_stub = """"NAME" IN ({})"""
stores = ','.join(["'{}'".format(x) for x in vals])
where = where_stub.format(stores)

# Import arcpy module
import arcpy
from arcpy import env

#workspace =  GetParameterAsText (0) ???
arcpy.CheckOutExtension("Network")

# Local variables:
in_network_dataset = "Transportation/Streets_ND"
outNALayerName = "BestRoute"


# Process: Make Route Layer
arcpy.MakeRouteLayer_na(in_network_dataset, outNALayerName, "TravelTime",
"FIND_BEST_ORDER", "PRESERVE_BOTH", "", "", "ALLOW_UTURNS",
"Oneway;RestrictedTurns", "", "", "", "")

# Process: Select
Stores = "Stores.shp"
Stores_Select = "Stores_Select_Output"
Expression = arcpy.GetParameterAsText(0)
vals = Expression.split(";")

where_stub = """"NAME" IN ({})"""
stores = ','.join(["'{}'".format(x) for x in vals])
Expression = where_stub.format(stores)


arcpy.Select_analysis(Stores, Stores_Select, Expression)