Thanks Sergey. The chr(0) solved the problem

>What parameters this DLL function expects? If it expects strings they have to be null-terminated strings. Try

strBaseDir="C:\test" + CHR(0)
>strCommand="SIGN" + CHR(0)
>

>>*this works
>>DECLARE integer FSL_Command IN rapidsign string strBaseDir, string strCommand
>>MR=FSL_command( "C:\TEST", "SIGN")
>>
>>*this does not work
>>DECLARE integer FSL_Command IN rapidsign string@ strBaseDir, string@ strCommand
>>strBaseDir="C:\test"
>>strCommand="SIGN"
>>MR=FSL_command(@strBaseDir, @strCommand)
>>
>>any explanation ?
>>
>>*****************************************************************************
>> the DLL specifications are :
>> * The functions have a PASCAL calling convertion (same as win APIs).
>> * The functions provided by this DLL are *NOT* reentrant.
>> * Many of these functions are blocking.
>> * The complex data types (structures) expected must have a member alignment of 1 byte (ie no padding).