Input Box repeatedly pops up

Hi All, I think I'm close to getting this code right - but the input box repeatedly pops up, and I need further code to stop the repetition after a user enters a value.

Basically - I am looking for an input box to pop up if a user inputs any value greater than 0 in cell A1, the input box then asks "Please enter the number of days you will be visiting this week" and inputs the value into A2. Thanks in advance for the help, I'm love learning this stuff and am pretty new.

Private Sub Worksheet_Change(ByVal Target As Range)
   If Worksheets("Sheet1").Range("A1").Value > 0 Then _
     Wkly = InputBox("Please enter the number of days you will be visiting this week")
     Cells(2, "A").Value = Wkly
End Sub