Calculate the percentage of order via in-store channel of customer "Medline".
Medline is the name of the customer; DIVIDE(COUNT(OrderNumber where Sales Channel = 'In-Store' and Customer Names = 'Medline'), COUNT(OrderNumber where Customer Names = 'Medline')) as percentage;
SELECT CAST(SUM(CASE WHEN T1.`Sales Channel` = 'In-Store' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1._CustomerID) FROM `Sales Orders` AS T1 INNER JOIN Customers AS T2 ON T2.CustomerID = T1._CustomerID WHERE T2.`Customer Names` = 'Medline '