creating a loop in vba for an excel macro

You could omit your code to only show the relevant part, or code a mockup macro to address only and only your problem.

Lets imagine your problem as a sub, which in this case is highly omitted:

Sub OmittedSub()
    ' Do stuff
End Sub

You can create new sub to call it many times, this new sub would be the one you would be calling instead:

Sub LoopOmittedSubs()
    Dim i As Integer

    ' Loop to call your macro routine multiple times
    For i = 1 To 100
        OmittedSub
    Next
End Sub

In case you would need to pass a value, for example your macro does not know which row to affect and you would need to tell it, you can pass the loop variable like this:

Sub OmittedSub(iRow As Integer)
    ' Do stuff for row number iRow
End Sub

Sub LoopOmittedSubs()
    Dim i As Integer

    ' Loop to call your macro routine multiple times
    For i = 1 To 100
        OmittedSub i
    Next
End Sub

This answer is the very basics of VBA. I dont know how to answer your question better without knowing what you already tried, how you tried, etc...

Raybarg provided you basic solution to that problem. I am not sure what do you mean by "certain cell", does it mean they have certain value or there are in regular order like A5, A10, A15?

In both cases you probably will use Raybarg's code and conditional statements.

You should include your code, it gives some hints on what you actually want to achieve and where is error.