Irwin Mortman claims that some Excel 5.0 Macro commands do not work in Mac OS 8. They are considered errors. For example, he had the problem when "asking a macro to pause and show a tool bar which can be clicked to continue the macro after user input."
When he contacted Microsoft technical support about this, they told him that they no longer support the Macro language in Excel and only support Visual Basic. (I have not confirmed that this is true.)