I don't think you can use transform in this case. Instead you can use Stuff().

?stuff('0800',3,0,'H')


>hi all,
>
>I have '0800' and i want '08H00' with transform function
>
>wait wind transf( "0800" , "@KR 99H99" ) is Not good ...
>
>
>thank a lot
>
>bernhart