Only Return Work Order Numbers After Amount Is Distributed

OK, one of the issues is that the date isn't a low enough granularity to do comparisons on, because there are multiple orders for the same item on the same day. You need another column, preferably numeric, which is unique for each row and can be used to determine the order. If you don't have one in the source data you can create one in Power Query. I did it by sorting the table by date and then work order with the M code below

let
    Source = Excel.Workbook(File.Contents(""), null, true),
    Sheet1_Sheet = Source{[Item="Sheet1",Kind="Sheet"]}[Data],
    #"Promoted Headers" = Table.PromoteHeaders(Sheet1_Sheet, [PromoteAllScalars=true]),
    #"Changed Type" = Table.TransformColumnTypes(#"Promoted Headers",{{"WorkOrder", type text}, {"PreviousIndexNumber", Int64.Type}, {"LinkToNextLine", Int64.Type}, {"Revision", type text}, {"StepNumber", Int64.Type}, {"UM", type text}, {"ItemDescription", type text}, {"Whse", Int64.Type}, {"ComponentItemNumber", type text}, {"QtyParent", Int64.Type}, {"UMconversion", Int64.Type}, {"UnitCost", type number}, {"ScrapPercent", Int64.Type}, {"ExtdQtyRequired", Int64.Type}, {"QtyIssued", Int64.Type}, {"QtyCommitted", Int64.Type}, {"DirectCosts", Int64.Type}, {"FixedOvhdCosts", Int64.Type}, {"VariableOvhdCosts", Int64.Type}, {"StdFixedOverheadAmount", Int64.Type}, {"StdVarOverheadAmount", Int64.Type}, {"WODueDate_CC", type date}, {"OrderStatus", type text}}),
    #"Sorted Rows" = Table.Sort(#"Changed Type",{{"WODueDate_CC", Order.Ascending}, {"WorkOrder", Order.Ascending}}),
    #"Added Index" = Table.AddIndexColumn(#"Sorted Rows", "Index", 1, 1, Int64.Type)
in
    #"Added Index"

Its just the last 2 steps you need really.

Once you have that column you can change the measure to be

Shortfall = SUMX(
	'WO2_WorkOrderMaterialDetail',
	VAR QuantityOnHand =
		RELATED( 'IM_ItemWarehouse'[QuantityOnHand] )
	VAR RequiredAmount =
		'WO2_WorkOrderMaterialDetail'[QtyCommitted]
	VAR CurrentIndex = 'WO2_WorkOrderMaterialDetail'[Index]
	VAR PreviouslyUsed =
		CALCULATE(
			SUM( 'WO2_WorkOrderMaterialDetail'[QtyCommitted] ),
			ALLEXCEPT(
				'WO2_WorkOrderMaterialDetail',
				'WO2_WorkOrderMaterialDetail'[ComponentItemNumber]
			),
			'WO2_WorkOrderMaterialDetail'[Index] < CurrentIndex
		)
	VAR AvailableStock = MAX( QuantityOnHand - PreviouslyUsed, 0 )
	RETURN
		MAX( RequiredAmount - AvailableStock, 0 )
)

This now uses the new index column and I also tweaked the return statement so that it won't return negative numbers.