Hello everyone! Basic functions for translation and validation of numbers to strings (and back) is very uncomfortable in terms of the fact that there is a lot to write, and they have their "eat." We can write the numbers in the hexadecimal system or brackets in exponential notation, etc. On the one hand it is good, but on the other can be a challenge. I wrote two functions that convert decimal integers of unlimited dimension from one representation to another. Can be useful for example to display the (Setup) LARGE_INTEGER or any other large (very large scale) numbers. Can somehow make a module for arithmetic operations with such numbers.
Option Explicit
Private Declare Function GetMem2 Lib "msvbvm60" (Src As Any, Dst As Any) As Long
Private Sub Form_Load()
    Dim Value() As Byte, Res As String
    StrToUI "1234567891011121314151617181920", Value
    Res = UIToStr(Value)
End Sub

' Convert unsigned integer from byte array to string (decimal system)
Private Function UIToStr(bValue() As Byte) As String
    Dim i As Long, f As Boolean, loc() As Byte
    loc = bValue
        i = Div10UI(loc)
        UIToStr = CStr(i) & UIToStr
        f = False
        For i = UBound(loc) To 0 Step -1
            If loc(i) Then f = True: Exit For
    Loop While f
End Function

' Convert unsigned integer (decimal system) from string to byte array.
Private Sub StrToUI(sValue As String, Out() As Byte)
    Dim i As Long, lpStr As Long, v As Integer, b(0) As Byte
    ReDim Out(0)
    If Len(sValue) Then
        lpStr = StrPtr(sValue)
        For i = 0 To Len(sValue) - 1
            GetMem2 ByVal lpStr, v
            v = v - &H30
            If v < 0 Or v > 9 Then Err.Raise 13: Exit Sub
            b(0) = v
            If i Then Mul10UI Out
            AddUI Out, b()
            lpStr = lpStr + 2
    Else: Err.Raise 5
    End If
End Sub

Private Sub AddUI(Op1() As Byte, Op2() As Byte)
    Dim i As Long, p As Long, o As Long, q As Long
    If UBound(Op1) < UBound(Op2) Then ReDim Preserve Op1(UBound(Op2))
        If i <= UBound(Op2) Then o = Op2(i) Else o = 0
        q = CLng(Op1(i)) + o + p
        p = (q And &H100&) \ &H100
        Op1(i) = q And &HFF
        i = i + 1
    Loop While CBool(o Or p) And i <= UBound(Op1)
    If p Then ReDim Preserve Op1(i): Op1(i) = p
End Sub

Private Function Div10UI(Value() As Byte) As Long
    Dim i1 As Long, i2 As Long, acc() As Byte, loc() As Byte, q As Long, p As Long
    For i1 = 0 To (UBound(Value) + 1) * 8
        Div10UI = (Div10UI * 2) Or p
        If Div10UI < 10 Then p = 0 Else p = 1: Div10UI = Div10UI - 10
        For i2 = 0 To UBound(Value)
            q = (CLng(Value(i2)) * 2) Or p
            p = (q And &H100) \ &H100
            Value(i2) = q And &HFF&
End Function

Private Sub Mul10UI(Value() As Byte)
    Dim i As Long, p As Long, q As Long
    For i = 0 To UBound(Value)
        q = (CLng(Value(i)) * 4 + Value(i)) * 2 + p
        p = (q And &HFF00&) \ &H100
        Value(i) = q And &HFF
    If p Then ReDim Preserve Value(i): Value(i) = p
End Sub
Good luck!