In the function SAP function name the parameter parameter name is specified as source field type with value source name-field name but the source source name must precede this function call.
In the function <SAP function name> the parameter <parameter name> is specified as source field type with value <source name-field name> but the source <source name> must precede this function call.
When you assigned a source field to a function parameter, you selected a source field from a source table that the ABAP program has not selected.
Select a source field from source tables above the SAP function in the ABAP program flow.