How To Run Replace On Varbinary Field

I need to run a replace on a varbinary field but I am unsure how. I have tried mulitple different methods and to no avail. I am stumped.

I have attached a zip folder that contains a spreadsheet that shows what I am trying to do. In the first tab it shows the SQL command I use to call the field I want to change. In this case it's the Content field and I am calling it using the content_key. As you can tell the content is stored as varbinary. In the second sheet, It shows this varbinary being converted to varchar(max) and it shows what the actual text says.

The table that this information is stored is is called digitalassetcontent

I need to remove the

Code:
<STYLE>H1{font-weight:bold}H1{font-size: 14pt}OL</STYLE><H1>Product Description</H1>

That is in front of the actual product description.

Somehow I need to run this command:

Code:
Update digitalassetcontent
set content = replace(CAST(content as varchar(max)), '<STYLE>H1{font-weight:bold}H1{font-size: 14pt}OL</STYLE><H1>Product Description</H1>','')

Where CAST(content as varchar(max)) like '<STYLE>H1{font-weight:bold}H1{font-size: 14pt}OL</STYLE><H1>Product Description</H1>%' AND content_key = 'desc214974236480438500781058983745755010'

This is the error message I get when running this code: Implicit conversion from data type varchar(max) to varbinary(max) is not allowed. Use the CONVERT function to run this query.

On the varbinary field. How do I do this?