Pop Up Message Box

I have following code to pop up the message box, but it does not pop up itself, I have to run the macros evry time. Is there any solution.

All I want if in Cell "C20" has the message " Check your Margin" than the message box pop up and should have the message as defined in my below code. Also, is this possible that the message should come in one box.

Private Sub Find_Criteria()
Dim i As Variant
Dim FindRange As Range
Set FindRange = Range("c10")
For Each i In FindRange
If i = "PLEASE CHECK YOUR MARGIN" Then
MsgBox "a) Check Provisional Sum allowances and Discounts"
MsgBox "b) Check with Brian if a base price review was required and missed"
MsgBox "c) Check for double ups in Timberline"
MsgBox "d) Check all big ticket items in Timberline ie. Trusses, bricks, plaster, paint and Site Works)"
MsgBox "d) Check if any items were underpriced in the contract and provide feedback to Brian"
MsgBox "e) Review and discuss any allowances with me." & " "

End If
Next i
End Sub