Create Drop-Down List Using Increasing/Decreasing Range

I have a list of jobs being displayed using the following code. All sheet names that start with AJ, CJ and PJ within the workbook are how the list is created.

Sub ListSheets()
Dim sht As Worksheet
Dim lRow As Long
Dim rCell As Range

With Sheet1

Set rCell = .Cells(2, 12)
End With

For Each sht In ActiveWorkbook.Worksheets
Select Case UCase(Left(sht.Name, 2))
Case Is = "AJ", "CJ", "PJ"
lRow = lRow + 1
rCell(lRow, 1) = sht.Name

Case Else
End Select
Next sht

End Sub

what i want to do is create a drop list within each job sheet within the workbook that will display the names of the jobs above. Now the thing is I cannot choose the range like normal from data - validation - list as I will not know how many job names will be displayed so I dont know how many cells to include in the range.