How to add +1 to a cell in Excel spreadsheet everyday if the cell has a value in it (if blank do nothing)

Question

I am making a spreadsheet in excel that is going to be used to track days passed since I have last contacted external POC's and send and email if 30 days have passed.

Basically, it is an excel spreadsheet using sheet1 and the sheet has the POC's email in (cell A2) and a command button in the next column (cell B2) that is on the physical spreadsheet that when pressed enters the number 1 in (cell C2). I am trying to make it so that if (cell C2) contains a value then every single day that passes automatically will make (cell C2's) value add +1 to it. Is this possible? I have tried looking around to find a point of reference to work from but cannot find anything. Anyone have any ideas or direction that they could point me towards to tackle this issue? In the end this will be used so that if cell C2 = 30 then I will get an email telling me that I haven't contacted them in 30 days.

Thanks in advance! I have included my working code below for the command button and the feature that sends an email if 30 days have passed if anyone else wants to do something like this.

The command button on the physical spreadsheets code is simply:

Private Sub CommandButton1_Click()
Range("C2").value = 1
End Sub

The code used to email me after 30 days have passed:

Dim xRg As Range

Private Sub Worksheet_Change(ByVal Target As Range)
    On Error Resume Next
    If Target.Cells.Count > 1 Then Exit Sub
  Set xRg = Intersect(Range("C2"), Target)
    If xRg Is Nothing Then Exit Sub
    If IsNumeric(Target.Value) And Target.Value > 30 Then
        Call Mail_small_Text_Outlook
    End If
End Sub

Sub Mail_small_Text_Outlook()
    Dim xOutApp As Object
    Dim xOutMail As Object
    Dim xMailBody As String
    Set xOutApp = CreateObject("Outlook.Application")
    Set xOutMail = xOutApp.CreateItem(0)
    xMailBody = "Hi there" & vbNewLine & vbNewLine & _
              "This is line 1" & vbNewLine & _
              "This is line 2"
    On Error Resume Next
    With xOutMail
        .To = "Email Address"
        .CC = ""
        .BCC = ""
        .Subject = "send by cell value test"
        .Body = xMailBody
        .Send
    End With
    On Error GoTo 0
    Set xOutMail = Nothing
    Set xOutApp = Nothing

End Sub

Answer 1

As per PEH's comment, change what the button does to implement a formula, not a number.

Private Sub CommandButton1_Click()
With Range("C2")
    .Formula = "=TODAY()-" & CDec(Date()-1)
    .NumberFormat = "General"
End With
End Sub