Create a text rule with this content and then apply the rule box. Apply the IDAUTOMATIONDMATRIX font to it and you should be good to go.
// Check treat strings as tagged text
//Replace "CNTL" with name of Field with ""
//Apply Rule as a text field and apply IDAUTOMATIONDMATRIX Font in 4pt
return MakeDataMatrixBarcode (Field("CNTL"), true, "TEXT", "UIC", "4", "NoFontTag", "IDAutomationDMatrix");