Chart the number of sales orders made per day or week or month and see how long the lag is between the first call and the resulting order. This will tell you over time how many sales calls your sales personnel need to make. To shorten this time period, do your homework upfront on who to call, who is more likely to buy, who is in the SIC codes that are shared by your current customer group. Over time you will have a good idea how many sales calls it requires to turn $1,000, $10,000 or $100,000 worth of incoming purchase orders.