Skip Cells

[mef1sto]

Hi guys and a Happy New Year!
Please give me a helping hand in this matter:

Public Sub Worksheet_SelectionChange(ByVal Target As Range)
If Not Intersect(Target, Range("A7")) Is Nothing Then
    Dim lastc As String, j, firstc As String, sstep
    Dim i As Long, s As Long, e As Long
    firstc = InputBox("Fill in the first cell ex. A7")
    If Len(firstc) = 0 Then Exit Sub
        j = InputBox("First cell value, ex. 1 sau 3 etc.")
        lastc = InputBox("Last cell in asc order, ex. A10")
    If Len(lastc) = 0 Then Exit Sub
        sstep = InputBox("Value to increment cells ex. 1 sau 2 sau 3 sau cum doriti")
    Dim index As Integer
' ?? HERE I NEED ANOTHER OPTION TO SKIP UPON 1 OR MORE CELL AND ADD THE +1 INCREMENT OF THE VALUE 
    If Len(sstep) = 0 Then Exit Sub
        For i = 1 To e Step -1
        Range(firstc) = j '
        Range(firstc + i, lastc + i).DataSeries Rowcol:=xlColumns, Type:=xlLinear, Step:=sstep, Trend:=False
        Next i
End If
End Sub

I would attach the .xlsm file but i donno how

Thanks for your aid!