stored procedure sanity check! [resolved]

[thebloke]

Guys, I need a fresh pair of eyes to look at this:

'vbscript
oConn.execute ("spVan_progress 2, " & session("van_id"))
'where van_id = 3

'sp
CREATE PROCEDURE spVan_progress
(
@step char(1),
@ref bigint
)
AS declare @sql nvarchar(500)

set @sql = 'update tblVan_counter set q ' + @step + ' = 1 where ref =  ' + @ref

execute sp_execute1 @sql
GO

should have the effect of...

spVan_progress 2, 3
'or
update tblVan_counter set q2 = 1 where ref = 3

The step variable is required so I can use the same sp to update any column. It should work (as far as I can see) but I get the error:

Microsoft OLE DB Provider for SQL Server (0x80040E07)
Error converting data type varchar to bigint.

The only bigint field in the table is 'ref' which I'm not altering. The q1 (q2, q3 etc) fields are bit.

Any clues?!