Attribute Rule to Calculate Site ID

[phess_luckstone]

So I am trying to create an attribute rule on a mosaic datasets footprint. What I would like to do is when a new raster is added to my mosaic dataset and the name of the raster is Site_FlightDate then depending on my site write the site code to a another field.  Any idea on how I could get the Name field to say if name is like Site1 auto-populate Site_ID field with 1234.

if ($feature["Name"] == 'SiteName') {
    return SiteCode #example 999;
} else {
    return Null;
}