I have following code that i wish to run on visible cells only.
the way i have it is slow can someone guide me in a better way to run
code on visible cells only.

Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual

Check = True: counter = 0: r = 50 ' Initialize variables.
Do ' Outer loop.
Do While counter < 1137 ' Inner loop.
r = 50 + counter 'start row
c = 14 'start Column

CloseStk = Cells(r, c).Value
calczero = Cells(r - 2, c).Value - Cells(r - 3, c - 2).Value
MinWks = Val(Cells(r - 3, 11).Value) / 4
ERQ = Cells(r - 3, 9).Value
Demand = Cells(r - 2, c).Value
Demand1 = Cells(r - 2, c + 1).Value
Demand2 = Cells(r - 2, c + 2).Value
Demand3 = Cells(r - 2, c + 3).Value
Demand4 = Cells(r - 2, c + 4).Value
MthsC = Cells(r - 3, 10).Value
Prod = Cells(r - 1, c).Value
OpenStk = Cells(r, c - 1).Value

If Cells(r, c).EntireRow.Hidden = False Then

If Cells(r - 3, 1).Value = "Y" And Cells(r - 3, 2).Value = 1 Then

If CloseStk = 0 Then
If MthsC = 1 Then
If Demand1 0 Then
Cells(r - 1, c) = calczero + (Demand1 * MinWks)
Else: Cells(r - 1, c).Value = calczero
End If

ElseIf MthsC = 2 Then

...... code goes on and on ........

End If

End If
End If
End If
counter = counter + 4 ' Increment Counter.
If counter 1137 Then ' If condition is True.
Check = False ' Set value of flag to False.
Exit Do ' Exit inner loop.
End If
Loop
Loop Until Check = False ' Exit outer loop immediately.

Application.Calculation = xlCalculationAutomatic
Application.ScreenUpdating = True


thanks for any help
Simon