Thanks Sergey (I did notice that when I tried to run my script after changing to real field names).

>Almost. SQL Server doesn't have logical data type. The bit data type is numeric.
>
>

>UPDATE [MyTable]
>SET [Field1] = @Field1,
>        [Field2] = @Field2,
>        [Field3] = CASE WHEN [Field4] = 1 THEN [Field3] ELSE @Field3 END
>

>
>
>>
>>

>>UPDATE [MyTable]
>>SET [Field1] = @Field1,
>>        [Field2] = @Field2,
>>        [Field3] = CASE WHEN [Field4] THEN [Field3] ELSE @Field3 END
>>

>>