Costing and Billing Mileage using a rate

I want to set up the following using iExpense and Project Billing:

iExpense template has the calculation for auto mileage reimbursment set up as .485 cents per mile.  When the user creates an expense report, they enter the number of miles and the system calculates the amount to be reimbursed to the employee. 

Example:

100 (miles) x .485 (cents per mile) = $48.50

On the project billing side I want to bill the customer at .85 cents per mile.  I have a bill rate schedule with the rate assigned to the expensditure type "Auto/Mileage".

Example: 

100 (miles) x .85 (cents per mile) = $85.00

Problem:

When the Expense Report transaction comes in from Payables the quantity and raw cost are both 48.50.  On the billing side, 48.50 is multiplied by the .85 which is obviously incorrect.