usertable error after adding a udf

I have a UI add-on that assigns values ​​to a UDT by usertable object of the DI API, the problem is generated after adding a UDF from SAP menu and try to assign a value from the DI. The error is Invalida Field Name

My question is, is necessary to wait a while until SAP records the new field to be accessible by usertable?

Any suggestions?

oUserTable.UserFields.Fields.Item("U_" + colName).Value = respuesta;