Here you go

Option Explicit

Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
    Dim r, c, u As Integer
    r = Target.Row
    c = Target.Column
    u = ActiveSheet.Cells.SpecialCells(xlLastCell).Row
    If c > 1 Or r > u Or VBA.UCase(Range("F" & r)) <> "PENDING" Then Exit Sub
    
    Dim Prompt          As String
    Dim Title           As String
    Dim strDate1       As String
    Dim Date1 As Date
    
    Prompt = "Enter date formatted: mm/dd/yyyy"
    Title = "[Please Enter Date]"
    strDate1 = InputBox(Prompt, Title)
    
    
    On Error Resume Next
    Date1 = CDate(strDate1)
    If Err <> 0 Or strDate1 = "" Then
        Exit Sub
    End If
    On Error GoTo 0
    Target(1, 1).Value = VBA.Format(Date1, "mm/dd/yyyy")
End Sub