Crystal Reports Formula Help

We have a report in Crystal Reports 11 that displays total item sales by month for the current year.  It includes parameter fields that allow users to select from one or more of the sales locations for the company.  The challenge is that for each item on the report it shows multiple lines for the monthly amounts (based on the various sales locations) instead of totaling the sales for each item for the month.  Here are the formulas in use:

Select Expert Formula:
{?Sales Location} = {oe_hist_prod.sales-location-key} and
{?Warehouse} = {oe_hist_prod.ship-location-key} and
{?Category} = {category.category-code} and
{oe_hist_prod.year} = 2015 and
{oe_hist_prod.period-type} = "Month"

Monthly Sales Formula:
TONUMBER(Split ({oe_hist_prod.units-shipped},";")[1])  <the 1 is for January, 2 for Feb, etc.>

Can anybody assist me in getting this to display the total for each item for all selected locations instead of multiple lines per item?