That's really simple to achieve.
You should create a new Panel with the following config:
Code:
var overlay = new Ext.Panel({
overlay: true,
centered: true,
width: 400,
height: 400,
layout: 'fit',
scroll: 'vertical',
dockedItems: [
{
xtype: 'toolbar',
dock: 'bottom',
defaults: {
ui: 'action'
},
items: [
{
text: 'Button1'
},
{
text: 'Button2'
},
{
text: 'Button3'
}
]
}
],
items: [
{
xtype: 'formpanel',
items: [
{
xtype: 'textfield',
label: 'Field1'
},
{
xtype: 'textfield',
label: 'Field2'
},
{
xtype: 'textfield',
label: 'Field3'
}
]
}
]
});