Trendline curved in wrong direction - actual built-in Excel solution?

[VeeRoc]

We have a data set with data tapering to zero for a facility closure. Is there a way to indicate to Excel that the trendline is another variety of Exponential, curving the other way? Every trendline fit I have tried, Excel either (1) assumes only an upward/increasing trend, as though it does not understand that something could possibly decrease (2) curves it the wrong way. The blue is hand-predicted datapoints, the orange is formula-generated by the equation y=13496.76-96.03672/2^(x/-1.688382). So of course I know what the best fit Trendline is, and have now created a workaround in the process. My question is, is there some setting in Excel that I have neglected, that is forcing it to adopt the orange trendline when there is clearly a much better fit possible? I feel like I am missing something terribly obvious. This adventure started with trying to force an intercept with a forecast trendline curved down with a known end-date, while of course Excel only allows an intercept to be forced on the other axis as far as I have been able to discover. Thanks!