Which formula do I use Excel for input and output of products?

I have a small table, where 'QTD_E' = Input and 'QTD_S' = Output, for each withdrawal of product quantity in 'QTD_E' I wanted to add how many products were taken out in 'QTD_S', what formula do I use for add a value in 'QTD_S' according to the removal of QTD_E's quantity values, ??