First of all it is easier to answer your question if you include a sample workbook to illustrate your question. However if I understand you correctly you have created a calculated field for the forecasted values. I would add an if statement which decides if you should display the forecasted value or the actual value.
The answer also depends on what your data source looks like? Do you have daily/weekly/monthly sales data?
We have FY sales data -Week,month,qtr,year are the level of data captured. Forecast values are also directly available. Im trying to arrive at a logic which can fix my above requirement. I tried If stmt but its giving an error (not to use Boolean values) in If stmt.
Is there any other logic to achieve the same.