Even if you hide the icon to Send to Excel, the user will still be able to right click and select 'Send to Excel' unless you disable the option in the Document Properties. One solution may be to just add in a warning message that the export is not advised.
If you don't like that option, maybe see about adding a macro to change the document properties to disable Exporting when your limit is surpassed and re-enable it when the user is back under the row limit. I haven't tried that before though so I don't know if that is easy or even possible. Somebody like swuehl or Gysbert Wassenaar would probably be able to tell you. See attached for example of first option. Note that I only used Count(Volume) to calculate rows since the sample data is so simplified; your equation would probably be a far more complex aggr() expression.