EXT JS IF FUNCTION

I have form which contains textfield. Need to run query if this textfield will contain value - 'test15'. Value 'test15' filled by system (read only for user)

             xtype: "textfield",
                fieldLabel: "...",
                name: "TRAIN1",
                readOnly: true,
                labelWidth: ...,
                width: ...,
                allowBlank: (...) ? false : true

so query should be like:

IF FIELD TRAIN1 = 'test15'
Order.query('Query1')[0].enable()