Search a String for 4 different variables then do a calculation based upon results

you want to create a measure, correct?

TPT =
IF (
    HASONEVALUE ( 'DeliveryPoint'[ProductCode] ),
    SWITCH (
        LEFT ( FIRSTNONBLANK ( 'DeliveryPoint'[ProductCode], TRUE () ), 2 ),
        "NI", DIVIDE (
            SUM ( 'Shifts and Events'[DeliveredQuantity(DU)] ) * 0.0000362318840580, [Trips(#)] ),
        "AR", DIVIDE (
            SUM ( 'Shifts and Events'[DeliveredQuantity(DU)] ) * 0.0000517063081696, [Trips(#)] ),
        "OX", DIVIDE (
            SUM ( 'Shifts and Events'[DeliveredQuantity(DU)] ) * 0.0000413907284768, [Trips(#)] ),
        "CO", DIVIDE (
            SUM ( 'Shifts and Events'[DeliveredQuantity(DU)] ) / 2000, [Trips(#)] )
    )
)

For a calculated column this code could be simplified

// Please do yourself a favour and
// first create a measure (can be hidden):

[DU Total Code-Agnostic] = SUM ( 'Shifts and Events'[DeliveredQuantity(DU)] )

// Then create a table that will map
// the 2-letter codes into factors
// (the numbers 0.0000362318840580...).
// This could be best done in Power Query.
// You can call the table CodeToFactorMapping.

// Then create measures (as many of them
// as the number of 2-letter codes, where
// xx stands for such a code, NI, OX...):

[DU Total xx] =
var __factor = <get the factor from the mapping table for code xx using lookupvalue>
return
	[DU Total Code-Agnostic] * __factor

// Your final measure would be something
// like this:

TPT =
var __productCode = SELECTEDVALUE ( 'DeliveryPoint'[ProductCode] )
var __2letterCode = LEFT ( __productCode, 2 )
var __total = 
	SWITCH ( __2letterCode,
	
        "NI", [DU Total NI],
        "AR", [DU Total AR],
        "OX", [DU Total OX],
        "CO", [DU Total CO]
    )
var __trips = [Trips(#)]
var __tpt =
	divide ( __total, __trips )
return
	__tpt

Please always try to keep your code clean. If there's something that repeats itself, make it into a unit on its own. You'll save yourself time and frustration and when a time comes to change, you'll need to make the change in one place only.

Best

Darek