Try

lcVar = ""
lcVar = NULL
lnExec = SQLEXEC(lnH, 'Exec sp_test ?@lcVar')


* In VFP9
lcVar = CAST(NULL AS char(7))

>
>With VFP 8 and SQL Server 2005 CTP:
>
>I need to pass a null value from VFP to call a SQL Server SP, but this parameter is declared as OUTPUT, and in fact, it must return a specific value.
>
>Let's assume this VFP code:
>

>lcVar = .NULL.
>lnExec = SQLEXEC(lnH, 'Exec sp_test ?@lcVar')
>

>
>When testing lnExec < 0, the error message is:
>1526 Connectivity error Microsoft][ODBC SQL Server Driver] Invalid character value for cast specification
>
>Is there any error in this logic? or any additional syntax required?
>
>The argument is declared like this:
>@cState char(7)=NULL OUTPUT
>
>
>The stored procedured runs without errors from SQL Query analizer and it accepts the null value, but I keep receiving the error message when trying from VFP.
>
>Thanks for any comment.
>
>Juan C.