Formula Help

Hello!

I can't figure out why this isn't working, anyone have a minute to help me out?

I have actual sales for elapsed months, and forecast sales for future months.  I am trying to sum actual + future month forecast to get a projected year end.  Ultimately, I want to be able to drill to style by month, and have it show the sales for actual or projected value.  If you are the year, and want to drill to month and see January sales, it will show you actual.  You can look at August sales, and see the forecast.

Here is the formula I am using:

IF ISNULL([TY Act Sls $])=TRUE THEN [TY FC Sls $]

ELSE [TY Act Sls $]END

Here is the result:

The YE forecast is a sum of Actual + FC, when I am looking for actual only.  Month 1, should be 111,774 but is summing Actual and FC SLS.

Where there is no value in Actual, the Act/FC value is correct, it matches the FC.

I am sure this is simple, and maybe I need to walk away for a minute, but if this is an easy solve and you have a minute to respond, that would be super.

TY!