DateDiff dynamic sql command

Hi All,

I have below function.

 
ALTER Function dbo.DynamicDateDiff
  (@Interval VarChar(2),
   @Date1 DateTime,
   @Date2 DateTime)
Returns Int
As
Begin
  Return (Select Case @Interval
                   When 'w' Then DateDiff(WEEK, @Date1, @Date2)
                   When 'y' Then DateDiff(YEAR, @Date1, @Date2)
                           When 'd' Then DateDiff(DAY, @Date1, @Date2)
                            When 'm' Then DateDiff(MONTH , @Date1, @Date2)
                   End
         )
End

Is it correct ?

And I want to call it from sub query.

declare @ToDate Date = '20200101'

select a.Item
 , (SELECT DBO.DynamicDateDiff(''d'', A.TglJatuhTempo, ''' + @ToDate + ''')) AS HariJatuhTempo
from ItemMaster a

Is the sub query correct ?

Thank you.