This is a rather quick and messy macro that leaves lots still to do, but you will get the idea.
It also presumes your original sheet("Sheet1") is sorted by LastRxNo.
If you had the ability to add and call a function in the SQLServer it would be a simpler, less error prone task.
hope this helps get you started. it outputs to a sheet called "summary"
Dim rx As String
Dim admTimes As String
Dim tmp As String
Dim i As Long
Dim LastRow As Long
LastRow = Sheets("Sheet1").Range("C" & ActiveSheet.Rows.Count).End(xlUp).Row
rx = ""
i = 1
For Each cell In Sheets("Sheet1").Range("C2:C" & LastRow)
If rx <> cell Then
rx = cell
i = i + 1
tmp = ""
tmp = cell.Offset(0, 11)
admTimes = admTimes + tmp + ", "
If cell.Offset(1, 0) <> rx Then
Sheets("summary").Range("A" & i) = rx
Sheets("summary").Range("B" & i) = Left(admTimes, Len(admTimes) - 2)
admTimes = ""