ALTER TRIGGER [dbo].[SRA_Log] 
   ON  [dbo].[tbl_SRA]
   AFTER UPDATE
AS 
	DECLARE @rec_id varchar(10), @field varchar(50), @value_before varchar(100), @value_after varchar(100), @usrn varchar(25), @SQL_STR varchar(100)
IF UPDATE(cpa_Decision) OR UPDATE (cpa_Case_From) OR UPDATE (cpa_Case_To) OR UPDATE ([cpa_Decision_Date]) OR UPDATE ([cpa_Leaf_No])
OR UPDATE ([cpa_Stage]) OR UPDATE ([cpa_Sample_Out]) OR UPDATE ([cpa_Change_Date]) OR UPDATE ([cpa_Decision_Old])
BEGIN
	SET NOCOUNT ON;
	Set @rec_id=(SELECT SMID FROM Deleted)
	Set @field=''
	IF (SELECT cpa_Decision FROM Deleted WHERE(SMID=@rec_id))<>(SELECT cpa_Decision FROM Inserted WHERE(SMID=@rec_id))
		Set @field='cpa_Decision'
	IF (SELECT cpa_Case_From FROM Deleted WHERE(SMID=@rec_id))<>(SELECT cpa_Case_From FROM Inserted WHERE(SMID=@rec_id))
		Set @field='cpa_Case_From'
	IF (SELECT cpa_Case_To FROM Deleted WHERE(SMID=@rec_id))<>(SELECT cpa_Case_To FROM Inserted WHERE(SMID=@rec_id))
		Set @field='cpa_Case_To'
	IF (SELECT cpa_Decision_Date FROM Deleted WHERE(SMID=@rec_id))<>(SELECT cpa_Decision_Date FROM Inserted WHERE(SMID=@rec_id))
		Set @field='cpa_Decision_Date'
	IF (SELECT cpa_Leaf_No FROM Deleted WHERE(SMID=@rec_id))<>(SELECT cpa_Leaf_No FROM Inserted WHERE(SMID=@rec_id))
		Set @field='cpa_Leaf_No'
	IF (SELECT cpa_Stage FROM Deleted WHERE(SMID=@rec_id))<>(SELECT cpa_Stage FROM Inserted WHERE(SMID=@rec_id))
		Set @field='cpa_Stage'
	IF (SELECT cpa_Sample_Out FROM Deleted WHERE(SMID=@rec_id))<>(SELECT cpa_Sample_Out FROM Inserted WHERE(SMID=@rec_id))
		Set @field='cpa_Sample_Out'
	IF (SELECT cpa_Change_Date FROM Deleted WHERE(SMID=@rec_id))<>(SELECT cpa_Change_Date FROM Inserted WHERE(SMID=@rec_id))
		Set @field='cpa_Change_Date'
	IF (SELECT cpa_Decision_Old FROM Deleted WHERE(SMID=@rec_id))<>(SELECT cpa_Decision_Old FROM Inserted WHERE(SMID=@rec_id))
		Set @field='cpa_Decision_Old'
		
	Set @SQL_STR=('SELECT ' + @field + ' FROM Deleted WHERE(SMID=' + @rec_id + ')') <= здесь нужно получить значение поля, которо подставляется из переменной @field
	Set @usrn=RIGHT(suser_name(), LEN(suser_name())-8)
	Set @usrn=(SELECT usr_Name FROM DIM_Users WHERE(usr_Login=@usrn))
	EXEC Logging_Changes @rec_id, 'tbl_SRA', @field, @value_before, @value_after, @usrn

SELECT @field FROM Deleted WHERE(SMID=' + @rec_id + ')

Set @field='cpa_Decision'