Adding a Custom Column with condition.

This is the code Csalinas144 

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("ddJLDoIwEAbgu7AmKTNtAQ+gK9m6IawMMRiFjS68vVNo6c8rodASvs6D1nVCSZqc++fwk2clg6y7ydDKKs54mubTtEnrhFeA2YNCEQchcx2JBnKRYUIMypRc3rgFR2Tk1e37ug9vrygEMoDMwrh9q67vrsNj8GpOz8Z6rCqjyV1yr/bd9p9QkZ4DMQRiiqjYIuNRrmgOJHPoXLlAYyNcJJ5qZwuNYGCnnaKCO86QsqMfOzZsjiULaCARdn2sy+2j/Zd0xHiZ4wYyQjgZpDfxCJhGZoCZ9SEkKM6ggkaS3ckSoT2CyzNyWbscXeFd8wc=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Purchase Order Number" = _t, #"Product Name" = _t, Gender = _t, Age = _t, Quantity = _t, Date = _t, #"Ship Date" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type date}, {"Ship Date", type date}}),
    #"Merged Queries" = 
        Table.NestedJoin(
            #"Changed Type",
            {"Product Name"},                               
            Prices, 
            {"Product Name"}, 
            "Prices", 
            JoinKind.LeftOuter
        ),
    GetPrice = 
    Table.AddColumn(
        #"Merged Queries",
        "Price",
        each 
            let
                varDate = [Date]
            in
            try
                Table.Max(
                    Table.SelectRows(
                        [Prices],
                        each [Date] < varDate
                    ), 
                    "Date"
                )[#"Price per Unit(US$)"]
                otherwise 0
    ),
    #"Removed Columns" = Table.RemoveColumns(GetPrice,{"Prices"})
in
    #"Removed Columns"

Note that the first record returned 0 becuase there was no price set for March 5, 2021. Prices didn't start until March 10.

Here is the PBIX though. It will be much clearer what I did since there are two tables involved.