Excel is an a$$, I've spent like decades with it lately trying to persuade it to use angular format for some geodetic fun, and nearly lost my hair. I even designed a new format in VBA there, which for me is a feat unheard of, but it kept on giving trouble anyway. What I would do, were I brighter, would be to define my own format in VBA. But since I'm not, I just transform everything to decimal system, do calcs therein and transform it back to hour format at output.
