Hi I have built an analysis cube and I am wondering how I can now somehow add in some kind of forecastinbg to it?

I have a time dimension in years, quarts, months, days.

Is there a way I can show forecasting calculations for future dates?

Sounds like what you're asking for is data mining

see

http://sqlmag.com/sql-server-analysis-services/understanding-time-series-forecasting-concepts

https://msdn.microsoft.com/en-us/library/ms169846.aspx