I would like to build timesheet solution. so each customer will have projects and projects will have timesheet.
so my relationship is like this
I have created an NEW table "Timesheet Invoice".
I will invoice timesheets monthly so so for each customer and for each month I will add an record in Timesheet Invocie table. so I will have something like this.
Customer ID Project ID Month/Year Total HoursCarry
123 3434 05/2018 £233.00
343 3343 06/2018 £230.00
My question is based around a field I will have called "Hours Carry".
"HoursCarry " will have an calculation which will get the previous month "total" and do some more calculation.
My question is how I can get the previous month total of specific customer and specific project. So or if I have customer '123' and project '343' I need to get the value of previous total so in this case I need £230.00. Once I can get the value I do furhter calculation and store new record for same customer and same project but for 07/2018.