Update a field in Deals module, when updating a field in Custom module

Update a field in Deals module, when updating a field in Custom module

Hello,

i have a custome module called "Descuentos y Plazos Esp"
I have a field in this custom module called "Plazo Concedido en días".

i need to update automatically a field in Deals module, with the same value. This field name is "PLAZO CONTRATO"

Example:
When "Plazo Concedido en días" is not empty, then update the field "PLAZO CONTRATO" with the same value.

Note: PLAZO CONTRATO field is in Deals module.

Thank you