I'm trying to summarize our sales totals by year and then by month, based on a joining of the year and month from a "current ready to ship" date column. I'm using this for the January 2017 total cell:
=SUMIF(yearmonth14:yearmonth51, LEFT(@cell, 9) = "2017 - 1", [P.O. AMOUNT]14:[P.O. AMOUNT]51)
This method works just fine, but I need to have it return nothing to the yearmonth column when what is in the date column is "TBD" or blank. I get #INVALID DATA TYPE if "TBD" or blank. This makes my totals also invalid.
It seems that Smartsheet can't pull data from a date column when what is in the date column isn't a real date. I tried a few if(isblank ideas, and iferror ideas, but I can't seem to find something that will work. I also tried making a text/number column and use something like =[CURRENT READY TO SHIP]14 but it also comes out #INVALID DATA TYPE
Maybe there is a simpler way to report monthly totals from a sheet like this, but I need help to see it. In total, I'm trying to report this information to a "sights" dashboard as a metric.

