This script will change the sms cache size.
Usage Example: cscript change-sms-cache.vbs 1000 d:
Note: size is in MB

On Error Resume Next
sSize = WScript.Arguments(0)
sLocation = WScript.Arguments(1)
Set oUIResource = CreateObject("UIResource.UIResourceMgr")
Set CacheInfo = oUIResource.GetCacheInfo

cacheInfo.TotalSize = sSize

if WScript.Arguments(1) then
CacheInfo.Location = sLocation
End if