Hi @Marc Fletcher‚ ,
we are using Fusion (you could use the API as well), to calculate the weekly normtime/capacity and then store that value in the extRefID field of the timesheet. You can then use that on a timesheet report or timesheet list to calculate the value. Here for example the missing normtime:
displayname=Missing Norm Time
textmode=true
valueexpression=IF(ISBLANK({extRefID})=false,SUB({totalHours},NUMBER({extRefID})),"")
valueformat=doubleAsDouble
Hope this helps!
Chris