Column widths Matrix

Hi,

I have a matrix table with three different headers like below, I am looking to fix the width of all the header 2 the same and the header 3. The matrix table has hundreds of columns so fixing all at once would be great.

I have tried the measure with a fixed legnth character and taking of word wrap and aut fix but that doesnt work as it is the 2nd and 3rd header I want to fix.

any help would be appreciated

thanks