A matrix is indexed like this: A(row,column). So to traverse a single column you leave the second value the same while changing the first value. If you want to find all the values in a column larger than a threshold you can do
You can easily count them by using sum
You can also replace those values easily like this
In that we are saying to set the values of A in the desired column that are larger than T1 are to be set to ten.
I am not what it is you are saying but here is a way to do what I think you are describing and if it is not quite right, hopefully I have given you what you need to figure out how to do it.
for n = 1:size(A,col)
if A(n,col) > T1 & sum(A(1:n-1,col)>T1)<T2
A(n,col) = 10;