Transpose Column Range Into Single Cell With Delimiter

I want to add a Punctation mark (comma), like this: ,
and also want to add punctation mark (colon), like this: :

In this moment I have below macro:

Public Sub CombineCells
Dim Combined As String
Combined = ""

For Each Cell In Selection
Combined = Combined & Cell.Value & ":"
Next Cell

Selection.Cells(1, 4).Value = Combined
End Sub

the effect shoud be like this:

before:
--A
1-C
2-D
3-E
4-F
Etc.

after transposed:
--D
1-C:D,E:F Etc.