Thank you all,
By the time my post was published, I already found the solution.
It's still great to be part of such a helpful community.
This is my final code in case someone will need something similar in the future:
SAPbouiCOM.Item oItem = oform.Items.Item("112");
SAPbouiCOM.Matrix oMatrix = (SAPbouiCOM.Matrix)oItem.Specific;
SAPbouiCOM.Columns oColumns = oMatrix.Columns;
SAPbouiCOM.Column oColumn = oColumns.Item("41");
SAPbouiCOM.Cell oCell = oColumn.Cells.Item(1);
SAPbouiCOM.ComboBox oComboBox = ((SAPbouiCOM.ComboBox)(oCell.Specific));
oComboBox.Select(sCardName, SAPbouiCOM.BoSearchKey.psk_ByDescription);
Dan