SQL Server has 2 time series algorithms: ARTXP and ARIMA.
You can achieve what you want with ARTXP.
ARIMA does not support cross-predictions (that is when one series values, such as inventory, affect another series predictions, such as sales).
You can read more information about it here
http://msdn.microsoft.com/en-us/library/ms174923.aspx
SQL Server does not implement ARIMAX
Tatyana Yakushev [PredixionSoftware.com]