dbrpcparam datalen problem

Hi, there

I have this data binding in the C code:
char szCounter[1025];
....
pSql->BindCharParam(12,"@Counter",szCounter,TRUE,1024);

I got a problem regarding the length of the datalen of dbrpcparam when
I tried to use it for the store procedure call:
dbrpcparam(..,SQLVARCHAR,..,1024, (BYTE *) szCounter)

When I used 1024 as the datalen, the store procedure call failed, but
if I changed the datalen to 256:
dbrpcparam(..,SQLVARCHAR,..,256, (BYTE *) szCounter),
it worked just fine!

The store procedure:
declare @Counter varchar(1024)
....
CREATE PROCEDURE ..,@Counter varchar(1024) output, ....

The databse is MSSQL.

Thanks!

Zhiyong Lu
guangxiren@xxxxxxxxx
.