matlab - Searching a matrix by row and column -

lets have matrix

dataset = [400,300,200,100,200,300,400;              1,  2,  3,  4,  5,  6,  7] 

this give me 2x7 array larger numbers on row 1 , smaller on row 2.

lets given number 200 , asked find numbers below 200 are. answer 3 , 5, because both correspond 200, how can code script?

>> dataset(2,dataset(1,:) == 200)  ans =       3     5