Hello,
I have BBA degree, management in IT, I work in sales and I am ms office/vba expert.
I've read your description, and I think I can write a macro for you which will change format [correct values] in your output excel file, so that you can use any formula you like on them. I think it's easier for you to use free tool you've mentioned for conversion, and then just apply macro for "updating" format / numbers in your excel file.
I would like to see your file prior to awarding / accepting project.
Please do check my past projects/reviews for your reference.
Looking forward hearing from you.