Hundreds of check boxes? Why does everybody always choose the hard way to do this kind of multiple selection? If you place all the equations in a multi-selection list box you have access through ListBox1.SelectedIndices(n) to exactly what you want without the need to run any kind of loop. You can then use a Select Case very simply

Code:
For n = 0 to ListBox1.SelectedItems.Count-1

Select Case ListBox1.SelectedIndices(n)

Case 0

'first equation

'etc.

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