Is it possible to do substring on multiple characters?

i’m having an issue writing down that code.

(
From a In dt_Internal
Let Date1 = a(“Date”).ToString
Let TransID = a(“Trans ID”).ToString
Let MSISDN = a(“MSISDN”).ToString
Let Type = a(“Type”).ToString
Let Channel = a(“Channel”).ToString
Let State1 = a(“State”).ToString
Let Amount = a(“Amount”).ToString
Let Target1 = a(“Target”).ToString
Let LongTransID =a(“Long Trans ID”).ToString
Let Details = a(“Details”).ToString
Let TraceNo = Details.Substring(9,6).ToString
Let UniqueIdentifier = TraceNo+ “-” + Target1.ToString
Let New String(UniqueIdentifier.Select(Function (x, i) If({5,2,3,1}.Contains(i), "*"c,x)).ToArray)
Select dt_InternalUID.Rows.Add( UniqueIdentifier, Date1, TransID, MSISDN, Type, Channel, State1, Amount, Target1, LongTransID, TraceNo ,MaskedUniqueIdentifier)
).CopyToDatatable