Link link existing user field matrix

experts,

Must link a link to an already existing column in an array.

It presented a reference error to object not definidad to instantiate object

  oMatrix = oMktForm.Items.Item ("38"). Specific

             oColumns = oMatrix.Columns

             oColumn = oColumns.Item ("U_US_Contrato")

             oLink = oColumn.ExtendedObject

             oLink.LinkedObject = 1250000025