error en trigger

Buenas Tardes Grupo...

Si me pueden ayudar con esta situacion...

CREATE TRIGGER mpTg_cambiofechas ON dbo.tbl_car_fechascobranza
FOR UPDATE
AS

insert into
tbl_car_cambiofechascobranza(strcampana,strcodcob,strcampomodifica,strvalorA
nterior,strvalornuevo,strusuario)

select del.strcampana,del.strcodcobranza,
case when update(dtmfechain21) then cast('dtmfechain21' as varchar(12))
when
update(dtmfechascierre) then cast('dtmfechascierre' as varchar(15)) end as
campo,
case when update(dtmfechain21) then del.dtmfechain21 when
update(dtmfechascierre) then del.dtmfechascierre end as valorant ,
case when update(dtmfechain21) then ins.dtmfechain21 when
update(dtmfechascierre) then ins.dtmfechascierre end as valnuevo,
ins.strusuario as usuario from deleted del inner join inserted ins on
del.strcampana+del.strcodcobranza=ins.strcampana+ins.strcodcobranza


CREATE TABLE [dbo].[tbl_car_cambiofechascobranza] (
[strcampana] [varchar] (6) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
[strcodcob] [varchar] (3) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
[strcampomodifica] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NOT
NULL ,
[intconsecutivo] [int] NOT NULL ,
[strvalorAnterior] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NOT
NULL ,
[strvalornuevo] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NOT
NULL ,
[strusuario] [char] (10) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
[dtmfecsis] [datetime] NOT NULL

CREATE TABLE [dbo].[tbl_car_fechascobranza] (
[strcampana] [varchar] (6) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
[strcodcobranza] [varchar] (3) COLLATE SQL_Latin1_General_CP1_CI_AS NOT
NULL ,
[strarea] [varchar] (2) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
[dtmfechaIn21] [datetime] NOT NULL ,
[dtmfechasCierre] [datetime] NOT NULL ,
[strusuario] [varchar] (15) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL
,
[dtmfecsis] [datetime] NOT NULL

el trigger me da este error
"syntax error converting the nvarchar value 'dtmfechain21' to a column of
data type int"


Mil Gracias...