Build complex formula for existing workbook

My name is Pilar, I am working on building an excel for tax calculation purposes and I am running into some trouble with a formula that I cannot build-in on my own. The excel is basically an annual gain/loss stock portfolio statement that takes the dollar amount of the purchase and sale proceeds and converting it into the official Mexican peso rate on those respective dates. The part that I am having trouble with is that the Mexican IRS requires that the cost of acquisition be adjusted by inflation so it yields the "Actualized Acquisition Cost” and that is the one that I must use to determine the gain or loss from the sale. The “Actualized Acquisition Cost” is calculated by taking the cost of acquisition of the stock plus the inflation for the period the stock was held. The inflation is equal to the sum of all the monthly inflations from the purchase date up to the month prior to the sale of the stock. Actualized Acquisition Cost = (Total inflation + 1) * Aquisition Cost The formula requires: For each individual stock acquisition, the sum of the inflations of each month from the purchase date up to the month prior to the sale date. The inflations would have to be looked-up and summed from a monthly inflation table. Depending on the purchase stock dates, the inflation summation will: 1) start in different months and, 2) sum different periods.