The following code takes many, many minutes to run on several hundred rows.
Does anyone have any suggestions that might speed it up?

Thanks in advance!

Option Explicit

Sub tester()
Dim i As Long
Dim area As String
Dim c As Range
Const sked = "0:30"

Application.ScreenUpdating = False

For i = 3 To Cells(Rows.Count, "C").End(xlUp).Row Step 1

If Cells(i, 1).Value < "CT" Then

area = Cells(i, "D").Value

Select Case area
Case "CR1"
For Each c In Range(Cells(i, "u"), Cells(i, "bg"))
If c.Text Like sked Then
c.Value = "CR1"
Else
c.Value = "X"
End If
Next c

Case "CR2", "CR3"
If Cells(i, "E").Value Like "*CR1*" Then
For Each c In Range(Cells(i, "u"), Cells(i, "bg"))
If c.Text Like sked Then
c.Value = "OTH"
Else
c.Value = "X"
End If
Next c
Else
Range(Cells(i, "u"), Cells(i, "bg")).Value = "X"
End If
Case Else
Cells(i, "U").Value = "X"

End Select

Else
Range(Cells(i, "u"), Cells(i, "BG")).Value = "X"
' GO TO NEXT

End If

Next i
End Sub