Crystal Reports crosstabs_creating an average field

Message

     hello!

I am working on a cross tab for which I have the following data

(my cross tab is located on the group footer) 

I am grouping on program_name

I want to see all the service codes, count of services for each service code, but i also the average count of services per client. 

I know that i will need a formula to devide the sum of date_of_service by distinct patient_id but how do i create this formula? 

then in the cross tab i will choose this formula to summerize. Once i do that i will edit the summary to be an average 

I first started with my crosstab in the report footer and i had the following formula. This worked but i need to have my cross tab on the group footer because i am pulling this data for multiple programs

Count ({billing_tx_history.date_of_service}, {Functional_Group.System_of_Care_Value})/DistinctCount ({billing_tx_history.PATID})

cross tab looks like this-----------------------------------------------------------------

Program Name Here 

                         count of services      Average Count of services per client
service codes 
301                            2,500                     20
331
361
351