Counting trips

Hello ninox team, i am working on a table where i put my trips, i want to count my trips within the month, the counter must reset at next month. For april, if i have 4 trips i want them named 1..4, in may i want them start over from 1 again.  I want to count all of my trips within the year. also, while counting, i want to categorize my trips. i have created a choice field, the code should be something like this

if number(month(tripdate))=4 and text(ChoiceField)="ChoiceA" then *counter 1 up*

coudn't figure out the code, how can i make this?

shn