Which Variables To Declare

As a rule which variables should I declare?


Sub checkPO()
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
Application.EnableEvents = False
Dim Rng As Range, MainSheet As Worksheet, item As Variant ', CurrWidth As Integer, UnitWidth As Integer

Set MainSheet = Sheets("Orders To Chase")
Set Rng = MainSheet.Range("B5", MainSheet.Range("B60000").End(xlUp))
totalqueries = MainSheet.Range("B5", MainSheet.Range("B60000").End(xlUp)).Cells.Count

UnitWidth = 282 / totalqueries

With progbar '\displays the please wait box
.Show False

.prog.Width = 0 '\ updates progress bar
.Repaint
End With

If I declare the variable my progress bar goes off screen. remove it and its back to within its box.

I haven't declared any of these variables either. Does this matter?


POnum = .Range("G5").Value
Supplier = .Range("A5").Value
Req = .Range("B5").Value
Ordered = .Range("E5").Value