Q:

Excel not responding when executing macro

I'm kind of new to programming and I don't really know much about debuggin in specific. I currently facing a problem with this code. It makes excel not responding for around 15 min when executed. 
What I´m looking for is to have date extracted from wb(ZTP Tracker Sharepoint) and look if there is an entry into another wb (Warning Tracker) within 5 days, then return Yes or No.
Have a look at the actual code:
Sub warning_lookup()

Sheets("Summary").Select

Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
Application.EnableEvents = False
Application.DisplayAlerts = False

For cell = 2 To 1001

    Value = Cells(cell, 3)
    If Cells(cell, 5) = "Yes" Or Cells(cell, 5) = "No" Then
        If Cells(cell, 5) = "Yes" Then
            For Each x In ['Warning Tracker'!A:A]
                If x.Value = Value Then
                    If Sheets("Warning Tracker").Cells(x.Row, 3) > Cells(cell, 4) - 1 And Sheets("Warning Tracker").Cells(x.Row, 3) < Cells(cell, 4) + 6 Then
                        Cells(cell, 6) = "Yes"
                    End If
                End If
            Next
        End If

        If Cells(cell, 5) = "No" Then
            Cells(cell, 6) = ""
        Else: If Cells(cell, 6) = isblank Then Cells(cell, 6) = "No"

        End If
    End If
Next

Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
Application.EnableEvents = True
Application.DisplayAlerts = True
Application.CutCopyMode = False

End Sub

A:

My best guess is that this line:
  For Each x In ['Warning Tracker'!A:A]

Is taking forever. You are saying "For each Cell in the entire column of A". In Excel 2007 or newer, that is over 1 million cells it has to check to see if x.value = Value. 
Change your for loop to something more restrictive:
  For each x in Range("A1:A50000")

You could also have the program figure out what that 50000 should be each time it runs:
 Dim lastRow as integer
 lastRow = Range("A999999").end(xlUp).Row
 For each x in Range("A1:A" & lastRow)
     ....

In this example the variable lastRow will hold the last row on the worksheet that has a value in Column A. 
Also, your syntax looks very odd on a few lines.

Else: If is sort of funky. That Colon should not be there. (perhaps this works, but I've never seen it before)
isblank is not a thing in VBA. isBlank is being treated as variable with no value in this case, so it might be working by accident...?
Your nested if statements can be combined into one. This isn't necessarly a bad thing, but all this nesting can lead to hard to read code.

Example of combining nested ifs:
If Cells(cell, 5) = "Yes" Or Cells(cell, 5) = "No" Then
    If Cells(cell, 5) = "Yes" Then

Could be:
If (Cells(cell, 5) = "Yes" Or Cells(cell, 5) = "No") AND Cells(cell, 5) = "Yes" Then

