Can we build a report to store previous values without a custom object?

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Hi

I have 5 custom fields in Contact Object related to billing details. In the workspace, I have added a tab "Bill Details" with the custom fields.

I would like to create a report, where in, when ever I change the values in the custom fields, the previous values should be shown in the report and the new values in those fields.

I know that billing details are generally achieved through creating a custom object. I would like to see if it can be achieved through custom fields itself.

So,  the design would be like a tab containing 5 custom fields (which will have latest bill details) and below those is a report with previous billing details. Is this possible?