Rename Part Of String From Combobox

I have a Userform (PictureViewer) with a.o. a combobox and a textbox on it. The combobox has a picturename with the full path, i.e. C:My DocumentsJohnMy PicsSummer VacationImg_0001.jpg. The textbox will have the replacement name for that picture entered in it while the picture is visible, i.e. Harry and Antoinette (no extension). Pictures get cycled on this Userform with a forward and backward button. When I click the forward button, the next picture opens up and the name of that picture replaces the previous name in the combobox. What I would like to do is on the click of a commandbutton, copy the string (full path) in the combobox to a column (A), starting at the first cell and in the column beside it (B) end up with the new picture name including the full path. In this case, that would be C:My DocumentsJohnMy PicsSummer VacationHarry and Antoinette.jpg. The next picture name I want to change would be in the cells below this. This could go on for many pictures. I have the macro to change the file names once when I have cycled through everything I want to change. Is it possible to do this in one click or do I have to split the drive name, all folder names and picture name, replace the picture name with the new name manually and concatenate it again? The depth of folders can vary of course. The macro for renaming is as follows

Sub RenameTheFiles()
Dim OldName As String
Dim NewName As String
Dim LastRow As Long
Dim I As Long
LastRow = Range("A65536").End(xlUp).Row
For I = 1 To LastRow
OldName = Range("A" & I).Value
NewName = Range("B" & I).Value
Name OldName As NewName
Next I
End Sub