I have two ranges, each containing a single cell (for example \"A1\" and \"C3\").
How do I get a new range containing all the cells between these two (\"A1:C3\")?
You can set the a new range in various ways. Below are a few examples. To get R1C1 format - I personally find it easier entering the normal formula and then using VBA to extract the R1C1 format required. See the debug.print statements below.
Sub test()
Dim rng1 As Range
Dim rng2 As Range
Dim newRng As Range
With Sheet1
Set rng1 = .Range("A1")
Set rng2 = .Range("C3")
Debug.Print rng1.FormulaR1C1
Debug.Print rng1.FormulaR1C1Local
'Method1
Set newRng = .Range(rng1, rng2)
'method2
Set newRng = .Range(rng1.Address, rng2.Address)
'method3 (Only works if rng1 & rng2 are single cells
Set newRng = .Range(rng1.Address & ":" & rng2.Address)
'method4
Set newRng = Union(rng1, rng2)
End With
End Sub