Can't increment Alphanumeric string by one

Attached file 160206 Text Autonumber.xlsm opens with Dashboard containing button that opens Order Form spreadsheet.

When the Order Form is called, I want the Macro to find the latest Job Number in the Job Database worksheet (e.g. "Job 5"), increment it by one as the next number in sequence ("Job 6"), enter that in the next row down, and copy it to Cell C3 in the Order Form.

The "click and drag" approach throws a "1004" error on the Selection Autofill line ("Autofill method of Range class failed")

Option Explicit

Sub NextOrder()

Dim b As Long, c As Long

Sheet1.Activate
b = Range("B65536").End(xlUp).Row
c = Range("B65536").End(xlUp).Row + 1

Selection.AutoFill Destination:=Range("B" & b, Range("B" & c)), Type:=xlFillDefault

Sheet2.Select
Range("C3") = Sheet1.Range("B" & c)

End Sub

Any pointers or suggestions received gratefully as ever.

Ochimus