B4R Question unable to change string variable

Sub Process_Globals
    Public Serial1 As Serial
    Private hours, minutes, seconds As Int = 0
    Dim alarmhours, alarmminutes, alarmseconds As Int = 0
    Private timer1 As Timer
    Private lcd As LiquidCrystal
    Dim pa0, pa1, pa2, pa3, buzzerpin As Pin
    Dim hour_changed, minute_changed, second_changed As Boolean = False
    Dim alarmhour_changed, alarmminute_changed, alarmsecond_changed As Boolean = False
    Dim mode_changed As Boolean = False
    Dim mode As Int = 0
    Dim alarm_active As Boolean = False
    Dim set As Int = 0
    Dim hours2 As Int = 0
    Dim day, month, year, set, day2, month2, year2, ret As Int = 0
    Dim counter As Int = 0
    Dim weekday As String
    
End Sub

Private Sub AppStart
    Serial1.Initialize(115200)
    Log("AppStart")
    timer1.Initialize("Timer1_Tick", 1000)

    
    pa0.Initialize(pa0.A0, pa0.MODE_INPUT_PULLUP)           'increment time depending on edit mode
    pa1.Initialize(pa1.A1, pa1.MODE_INPUT_PULLUP)           'select edit mode
    pa2.Initialize(pa2.A2, pa1.MODE_INPUT_PULLUP)           'decrement time depending on edit mode
    pa3.Initialize(pa3.A3, pa3.MODE_INPUT_PULLUP)
    buzzerpin.Initialize(3, buzzerpin.MODE_OUTPUT)
    buzzerpin.DigitalWrite(False)
    
    pa0.AddListener("pa0_StateChanged")
    pa1.AddListener("pa1_StateChanged")
    pa2.AddListener("pa2_StateChanged")
    pa3.AddListener("pa3_StateChanged")
    
    lcd.Initialize(8, 255, 9, Array As Byte (4, 5, 6, 7))
    lcd.Begin(16, 2)
    lcd.Blink = False
    timer1.Enabled = True
    
    'set time and alarm initial values
    hours = 10
    minutes = 17
    seconds = 00
    alarmhours = 7
    alarmminutes = 45
    alarmseconds = 0
    day2 = 7
    day = 7
    month = 05
    year = 23
    counter = 3
    weekday = "Su"