Passing and nvarchar(Max) parameter form Access 2013 to a SQL Server SPROC?

I am writing a routine in my Access 2013 front end that calls a SPROC on SQL Server.  One of the params is a user comment that is defined as nvarchar(max) on the SQl side.

I have written access routines that call SPROCS, passing string variables but they are of a defined length.  A param statement passing to a field defined as nvarchar(30) in SQL looks like this:

    Set param6 = .CreateParameter("passedUserName", adVarChar, adParamInput, 30, passedUserName)
    .Parameters.Append param6

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What would the syntax be when passing a param defined a nvarchar(max) in the SPROC?

I'm temporarily using

    Set param6 = .CreateParameter("passedUserName", adVarChar, adParamInput, 1000 , passedUserName)
    .Parameters.Append param6

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but that has a fixed length of 1000.