To convert amount to text, you can use the amount_to_text method defined in openerp/tools/amount_to_text_en.py

Create a field which will store text value of amount. You can either create char or text field.

'text_amount': fields.char("Text Amount", size=100)

or

'text_amount': fields.text("Text Amount")

Now write a on_change method which will be called when you change the value of amount field. First add on_change in your xml where your amount field is.

Like this:

<field name="your_amount_field" on_change="onchange_amount(your_amount_field)"/>

Write the following code inside your class in your py:

from openerp.tools import amount_to_text_en

def onchange_amount(self, cr, uid, ids, amount):
    text_amount = amount_to_text_en.amount_to_text(amount, 'en', 'EURO')
    return {'value': {'text_amount': text_amount}}