How to calculate Total Count of Tran datetime

Dear Expert,

I am new to business object and need your help to create a variable to count Total Tran datetime of a Customer ID. I want to create this variable to identify how many times a day customer did the transaction to our Store.

Example :

Here XYZ customer made Total 5 Transaction on 10-Oct-2015

So I want to create a variable which will count the total tran date time on a business Day for a Customer.

Please help.

Thanks in Advance