Hi,
Sorry for the delay, called away.
Not sure what your trying to achieve, but maybe this:-

#define REF "something"
#define INP "something else"
#define OUT "anything"

? INP, REF, OUT

>No...
>This source code save as xparam3.prg and recompile it. Look to err file.
>

>#define INP
>#define REF
>#define OUT
>#define CHNG
>
>PROCEDURE test(INP REF OUT CHNG luPar1, REF luPar2)
>

>
>Result:
>

>PROCEDURE test( REF  CHNG luPar1,  luPar2)
>Error in line 7: Syntax error.
>

>
>Why don't replace constants REF and CHNG? But constants INP and OUT are replaced.
>
>MartinJ
>
>>Are they keywords or system variables.?
>>
>>>Run this example:
>>>

>>>#define INP
>>>#define REF
>>>#define OUT
>>>
>>>? INP REF OUT && Variable 'REF' is not found.
>>>? INP REF     && Variable 'REF' is not found.
>>>? INP
>>>
>>>? INP OUT REF && Variable 'OUT' is not found.
>>>? INP OUT     && Variable 'OUT' is not found.
>>>

>>>
>>>
>>>Why preprocesor ignoring each second constant at compiling?
>>>
>>>MartinJ