I dug out some SP code that illustrates this:

CREATE PROCEDURE CustomerInsert                   
	@FName		varchar(50),
	@LName		varchar(50),
	@Title		varchar(50) = NULL,
	@EMail		varchar(100) = NULL,
	@UserName	varchar(50),
	@Password	varchar(50)
AS
INSERT INTO [mark].[dbo].[Customer]
(	
	[FName],
	[LName],
	[Title],
	[EMail],
	[UserName],
	[Password]
)
VALUES 
(
	@pcFName,
	@pcLName,
	@pcTitle,
	@pcEMail,
	@pcUserName,
	@Password
)

I do not remember the syntax for the SQLEXEC() but I did pass the values to the SP by reference as indicated by the @ symbols in the above values.