How to change values meeting certain criteria to NaN... in certain columns only

I have a large matrix with 96 columns and thousands of rows. I would like to find all values values larger than 100 in even-numbered columns (2, 4, 6...) and replace them with NaN.

I know of:

A(A(:,2)>100,2) = NaN;

How can I make it work with multiple columns (:,2:2:end)?

Answer 1

[madhan ravi]

B=A(:,2:2:end);
idx=B>100;
B(idx)=NaN;
A(:,2:2:end)=B

[Corymbiamaculata]

Thanks! I should have thought of that.

PS The avatars :)