Add field to payment option

[prehn]

Hello all!

I need to add an field to one of my payment method (vm standard payment plugin). If the customer wants to pay by invoice they will have to put in the social security number, but only if the choose to pay with invoice. Those who would like to pay with my other options should not be forced to enter their social security numbers.

Is there any way to do this, to add a field that needs to be filled in only if they choose a specific payment option?

Hope you understand what i mean.

Regards

Nielsen