Predefined value when choosing a value

within a cdt I have a group with two groups inside and in each group a user.
apart form a form with two fields. in the first field there is a pickerFieldGroups and within the a groupfilter. 
the other field is where I want the user that comes associated with the group I chose in the first field to appear.

Thanks



load(
 a!formLayout(
 label: "",
 contents: {
 a!columnsLayout(
 columns: {
 a!columnLayout(
 contents: {
 a!textField(
 label: "Oficina solicitante",
 labelPosition: "ADJACENT",
 saveInto: {},
 refreshAfter: "UNFOCUS",
 required: false,
 readonly: true,
 validations: {}
 ),
 a!columnsLayout(
 columns: {
 a!columnLayout(
 contents: {
 a!textField(
 label: "Territorial",
 labelPosition: "ADJACENT",
 value: ri!nuevasSolic.territorial,
 saveInto: ri!nuevasSolic.territorial,
 refreshAfter: "UNFOCUS",
 required: true,
 validations: {}
 )
 }
 ),
 a!columnLayout(
 contents: {
 a!richTextDisplayField(
 label: "",
 labelPosition: "ABOVE",
 value: {
 a!richTextIcon(
 icon: "tags",
 link: a!safeLink(
 label: "Company web site",
 uri: "http://www.appian.com"
 )
 )
 },
 align: "LEFT"
 )
 }
 )
 }
 ),
 
 a!columnsLayout(
 columns: {
 a!columnLayout(
 contents: {
 a!textField(
 label: "Persona de contacto en oficina",
 labelPosition: "ADJACENT",
 value: ri!nuevasSolic.personaContactoOficina,
 saveInto: ri!nuevasSolic.personaContactoOficina,
 refreshAfter: "UNFOCUS",
 required: true,
 validations: {}
 )
 }
 ),
 a!columnLayout(
 contents: {
 a!richTextDisplayField(
 label: "",
 labelPosition: "ABOVE",
 value: {
 a!richTextIcon(
 icon: "user",
 link: a!safeLink(
 label: "Company web site",
 uri: "http://www.appian.com"
 )
 )
 },
 align: "LEFT"
 )
 }
 )
 }
 ),
 
 }
 ),
 
 }
 ) 
 },
 buttons: a!buttonLayout(
 primaryButtons: {
 a!buttonWidget(
 label: "Enviar",
 value: true,
 saveInto: {},
 submit: true,
 style: "PRIMARY"
 ),
 a!buttonWidget(
 label: "Cancelar",
 value: true,
 saveInto: {},
 submit: true,
 style: "NORMAL",
 validate: false
 )
 },
 secondaryButtons: {}
 )
 
)

)