Add content to several custom fields by class?

Hello, Imagine a sentence like < span class="my-company">This Company< / span > is hiring a person for  < span class="my-job">this job< / span > in < span class="my-city">this city< / span >. How can I add custom fields like:

• company_name => %%class_my-company%%
• job => %%class_my-job%%
• city => %%class_cmy-city%%

Thanks for the help.