The thing that is being missed here as far as i can see is:

The code works perfectly but does not show the user visually what is happening, what we get is Cel holding the address of the goal when the code has run.

I was thinking (post 9) that it would be nice if the user could see the path visually.

Sub PATHer()
  Dim Cel As Range
  Set Cel = Range("C3") 'set starting cell here
  Do While Cel.Address <> "$Q$18"  'Insert end cell address here in $A$1 style
    Select Case Cel.Value
      Case "R": Set Cel = Cel.Offset(0, 1)
      Case "L": Set Cel = Cel.Offset(0, -1)
      Case "U": Set Cel = Cel.Offset(-1, 0)
      Case "D": Set Cel = Cel.Offset(1, 0)
    End Select
    Cel.Interior.Color = vbRed
  Loop
End Sub