Basic authentication of SOAP service without external system key in admin console

Is it possible to authenticate the web service without Scsfield (i.e., not from external system key in admin console)? So, I have a requirement like parsing a spreadsheet which has service authentication credentails (get as Text variables) and use them while calling at web serivce (SOAP). The reason is - I don't want to keep the credentails under third party credentails in admin console as many people in the team have got the access to admin console. Please help.

Thanks

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