Hint: There is a column named “pma_timestamp” in table “table_a”, but it cannot be referenced from this part of the query

hi i want to use a user defined function so that while inserting values in column i want to insert last_day of the month in one column by referencing other column in same table.

my code is-

insert into table_A (id,pma_timestamp,monthend) values (103,’2017-08-15′,last_day(pma_timestamp));

but getting error. how to resolve this