Performance Optimisation - vba

Question

I have this bit of my code which takes like 90 % of the runtime.
There are about 8000 rows and information are stored in column A. This bit of code is splitting this information in the other columns.
It takes approximately 15 mins to run ( :O ).
Any suggestions on how to improve the performance ?
For i = 2 To Row_Number ' Loop for each row
If InStr(Cells(i, 1), "//") = 0 Then ' This means that if // appears somewhere in the text we delete all the rows (including this one) (see Else :) and stop the loop
j = 1
Do Until Mid(Cells(i, 1), j, 1) = ";"
j = j + 1
Loop
LongVIN = Mid(Cells(i, 1), 1, j - 1)
k = j
j = j + 1
Do Until Mid(Cells(i, 1), j, 1) = ";"
j = j + 1
Loop
Cells(i, 3) = Mid(Cells(i, 1), k + 1, j - k - 1) ' Model
k = j
j = j + 1
Do Until Mid(Cells(i, 1), j, 1) = ";"
j = j + 1
Loop
Cells(i, 4) = Mid(Cells(i, 1), k + 1, j - k - 1) ' Dealer
k = j
j = j + 1
Do Until Mid(Cells(i, 1), j, 1) = ";"
j = j + 1
Loop
k = j
j = j + 1
Do Until Mid(Cells(i, 1), j, 1) = ";"
j = j + 1
Loop
Cells(i, 6) = Mid(Cells(i, 1), k + 1, j - k - 1) ' Region
k = j
j = j + 1
Do Until Mid(Cells(i, 1), j, 1) = ";"
j = j + 1
Loop
Cells(i, 7) = CDate(Mid(Cells(i, 1), k + 1, j - k - 1)) ' Retail Date
k = j
Cells(i, 5) = Mid(Cells(i, 1), k + 1, Len(Cells(i, 1)) - k) '(Len - (k+1) +1) Dealer Name
Cells(i, 1) = Mid(LongVIN, 1, 10)
Cells(i, 2) = Mid(LongVIN, 11, 7)
Else:
Range("A" & i & ":A" & Row_Number).Delete 'ClearContents
Exit For
End If
Next i

Answer 1

You should see a significant boost in performance by storing the data in an array, operating on the array, and storing the data back into the spreadsheet.
Something like:
Dim data As Variant
Dim result As Variant
data = Range(Cells(2, 1), Cells(Row_Number, 1))
Redim result (1 To Row_Number, 1 To 7) As Variant
Now instead of reading from Cells(i, 1), you read from data(i, 1) and instead of writing to Cells(i, n) you write to result(i, n).
And at the end of your code:
Range(Cells(2, 1), Cells(Row_Number, 7)) = result