How to pass a data from renderDT function to renderInfoBox function ?

Suppose I have a renderDT function (in Server) from where I am passing a dataframe as an Output to the DTOutput (in UI). It (renderDT in Server side) has a column called Safety Stock. I have certain input parameters which if I change (inputSlider) then the Safety Stock values will change. Thus the Safety Stock is reactive in nature (and thus it is being calculated inside the renderDT function).

I have another renderInfoBox function wherein I want to display the mean of the previously calculated Safety Stock.

But the problem is I am not able to use the value of the reactive Safety Stock (in renderDT) in the renderInfoBox function. How can I do it ?