Lets say your Actual Data is coming from Data base and you have a sheet where your forecast data is there , So yes you can do this ,What you need to do create a local connection in scripting part and import that foretast sheet and go to UI and compare it.
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If you have transaction data at more granular like transaction level
i.e TranNo/DocumentNo | Itemcode | ItemVariant | Location | Date | Month | etc | etc | ActualValue | ActualQty
and you have your forecast at Month level for each of Location and Product in Excel
Then upload that excel values into app with same column name as like transaction data
Product | Location | ForecastValue | ForecastQty
Qlik sense will automatically form the synthetic key in the so that when you do visualizations with those field (ex) a table/ pivot table you will be able to compare the Actual vs Forecast against a common dimensions.
Hope this Helps you