Forecasting / Capacity Planning Template

I have historical data that has total sales, month, time spent to achieve sales and name of each salesperson. I would like a excel template that once data is entered it will forecast what is needed to achieve a goal. Specifically, Prior year has over 50,000 in sales. Need to achieve 100,000 in sales in next year. The prior year (say 2015) achieved 50k in sales with 8 people. It would be simple to say with 100k with 16 people. However, excel template should account for seasonality. Also trend for what each salesperson will achieve based on 2015 and forecasting their performance for 2016.