How to add record to Complex Store

[Designworxz]

How can we add record to a complex store.

Ext.regModel("model", {
fields: [
"Department",
"Pic",
{ name: "Employee", type: "auto" }
]
});
Store = new Ext.data.Store({
model: "model",
}
});

Store.add(//DepartmentName);

Store.getAt(0).set('Employee",//Employee record);
This one works.

But if i try to add new Employee record again at index 0 it replaces old employee
How can i add multiple Employee at index 0 of Store?

[mitchellsimoens]

Store.insert accepts an index as it's first argument.

[Designworxz]

Am doing this which works fine, but am using same store in Xtemplate on other view where i cant see data coming.

if(Store.getAt(0).data.Employee=== undefined)
{
Store.getAt(0).set("Employee",[ rec.data]);
}
else
{
Store.getAt(0).data.Employee.push(rec.data);
{

'<tpl for=".">',
'<tpl for="Employee">',
'{Name}',
'</tpl>',
'</tpl>'

Do you have any other method to do that as Employee field can have multiple objects.