Excel 97 This workbook contains...

Question -

I was writting a program in Excel 97 VBA and tested it with Macro Virus Protection enabled, and declined to enable Macros.

After the standard warning, I got the following message:
"This workbook contains a type of macro (Microsoft Excel Version 4) that cannot be disabled."

It got me curious.
Anyone have some comments on which part of my code could be creating this.

I have VBA code stored in all three components of VBA - Microsoft Excel Objects, Forms and in Code modules. But I haven't done anything with Excel 4, XML or any former Excel macro components that I know of.

I thought it might have been the code stored under the workbook sheets, but they all belong to my Control buttons, certainly not a feature in prior Excel Versions.