CREATE TABLE IDDemo
( pk_ID Integer IDENTITY(1,1)
, Textdata Varchar(100) )

EXEC ('SET IDENTITY_INSERT IDDemo ON;INSERT IDDemo (pk_ID, Textdata) Values (4, ''This works too'');SET IDENTITY_INSERT IDDemo OFF;')

SELECT * FROM IDDemo

CREATE TABLE IDDemo
( pk_ID Integer IDENTITY(1,1)
, Textdata Varchar(100) )

DECLARE @sql varchar(max)
declare @tablename varchar(30)

SET @sql = 'SET IDENTITY_INSERT @TheDynamicTableName ON;INSERT @TheDynamicTableName (pk_ID, Textdata) Values (4, ''This works too'');SET IDENTITY_INSERT @TheDynamicTableName OFF;'
SET @tablename = 'IDDemo'

SET @sql = REPLACE(@sql,'@TheDynamicTableName',@tablename)
PRINT @sql
EXEC (@sql)

SELECT * FROM IDDemo