This piece of code creates a couple of comboboxes dynamically. I hope this is what you was looking for.
for (var i=0; i < 8; i++) {
Ext.create('Ext.form.ComboBox', {
fieldLabel: 'Combobox '+i,
store: ['Option1','Option2'], //better to use a dynamic store
renderTo: Ext.getBody()
});
};