Table field validations on add row button click

we have a structure as bellow –

1) I have a table fragment with one table(test1 table) which have numeric field and under that table we have another table (test2 Table) with one row of input fields.

2) When I hit add new row button then it will add the complete table fragment.

Requirement –

a) If table fragment added more then three time make the test2 table is required for top three numeric field values of test1 table.