Problem with sum(select(and)))

[HoeySho]

i will two table,
table one called student contain student details
table two is a payment_log contains payment amount, which month they paid for, date and time.

i want to create a virtual column in table student which can calculate each student’s monthly pay amount, because some of them may pay two / three times.

so a select function with two filter is my thought to this. I tired to write the formula, but it doesnt work…

Sum(select(and(payment record[paymonth] = “Mar” , payment record[payment], [name]=[_thisrow].[id])))

the error display that Cannot compare List with Text in (Payment record[Paymonth] = “Mar”)

anyone can help me?Thank you!