Writing electronic files to images for the purposes of redaction is never ideal. Excel files can lose some of their functionality and non-confidential information they were meant to convey can be lost.
On this site, http://www.thepaynegroup.com/products/redact/ , you can download a trial version of a program called Redact Assistant which will redact terms from Word and Excel files. This is put out by a vendor called the Payne Group. Payne Group also markets a widely used program called MetaData Assistant, so it should be good at creating software that scrubs an electronic file of the information you want to redact.
The trial version lasts for 30 days, and a license only costs $45. An easy enough cost to justify if you have a redaction project.
The screen grab below shows what the plug-in for Excel looks like. After installation a separate tab is added to Word named 'Redact'. You can either select terms to be redacted with your mouse, or you can search for a list of terms that you want redacted.
I tested it out and confirmed that it leaves a redacted Excel file with at least basic functionality.
Redact Assistant isn’t just a plug-in. It also runs as a separate application, so you can redact specified terms from multiple files in one shot. Pre-defined search terms can be selected for credit card numbers, social security numbers, email addresses and telephone numbers.