ComboBox - using a template / expression for displayValue?

[Wolfgang]

Hello,

Short: How can one assign an expression or template for 'displayField' in a combobox?

Example:
i have an editorgrid where a use a combobox as an editor to select employees.
The grid itself has only the id of the employee, so the CB has its own datastore.

Because i would like to display the entire name and the DS of the combobox contains firstname, lastname seperate, i need to calculate the final 'name' to display it.

Within the grid, i use a custom renderer like this (getting the vales from the CB datastore based on the id)

...
return dsRecord.get('vorname') + ' ' + dsRecord.get('nachname');
...


Now for the selection i found an undocumented option called 'tpl' to define a template for the selection box. So my Cb looks like:

new Ext.form.ComboBox({
typeAhead: false,
triggerAction: 'all',
lazyRender: true,
store: dsMitarbeiter,
displayField: 'nachname',
valueField: 'id',
mode: 'local',
tpl: new Ext.Template('<div>{vorname} {nachname}</div>')
})


But, i have not found a way to set a template or expression for 'displayField'.
So when doubleclick the cell within the grid, the input field shows only the value of 'displayField' not the entire name.

So the grid shows:
beforeedit: 'Donald Duck'
during edit: 'Duck'
during edit combo box selection: 'Donald Duck'
after edit: 'Donald Duck'

Any help/comment is appreciated...

Note: To calculate the entire name on the server side is not an option, because this is a conceptional issue.