Filtering Denominator Based on Data From Another Column

The expected output for Texas, for example, would be all of the Product 6 volume in Texas as the numerator (1/4 account 1 & 1/11 account 3) = 40. Divided by all of the Category A volume that would have been received on or after the initial shipment of product 6 (1/4 Account 1, 1/11 Account 1 & Account 3) = 32+109 + 86 = 227. The share of product 6 in stores selling in Tx would be 40/227 or .176. Since Account 1 & 3 have received product 6, their Category A volume will continue to add to the denomintor every week from that point on. We want to understand how our product compares to the total category on in the stores that are carrying it with the assumption that they will order more of it when they are close to selling out.