Try setting the custom JavaScript verification to this:
var rows = $('input[name="hid_row_list_[% QuestionName() %]"]').val().split(',').map(Number);
var prev = SSI_GetValue('[% QuestionName() %]_r' + rows[0] + '_c1');
for (var r = 1; r < rows.length; r++) {
var curr = SSI_GetValue('[% QuestionName() %]_r' + rows[r] + '_c1');
if (curr < prev) {
strErrorMessage = 'Error message.';
}
prev = curr;
}