Option Explicit

#If VBA7 And Win64 Then
Private Declare PtrSafe Function GetTickCount Lib "kernel32" () As Long
#Else
Private Declare Function GetTickCount Lib "kernel32" () As Long
#End If
Sub test_ENVIROMENT_READ_WRITE()
Dim sEnvType$: sEnvType = "USER" ' "SYSTEM" [default value can be omitted] | "VOLATILE" | "PROCESS" | "USER"
Dim sEnvName$: sEnvName = "myDATA"
Dim sEnvData$: sEnvData = "test-test-test"
Dim lTimer&, t&
With CreateObject("WScript.Shell").Environment(sEnvType)
Debug.Print "Environment(""" & sEnvType & """).Count = " & .Count
    lTimer = Timer
    t = GetTickCount
    .Item(sEnvName) = sEnvData   ' Create User's Environment
Debug.Print "Create Duration = " & Timer - lTimer & " s" ', "Count = " & .Count
Debug.Print "- " & (GetTickCount - t) / 1000 & "s"
Debug.Print "Environment(""" & sEnvType & """).Count = " & .Count
    lTimer = Timer
    t = GetTickCount

    sEnvData = .Item(sEnvName)   ' Read User's Environment
Debug.Print "Read Duration = " & Timer - lTimer & " s", "Value = " & sEnvData
Debug.Print "- " & (GetTickCount - t) / 1000 & "s"

    lTimer = Timer
    t = GetTickCount
    .Remove (sEnvName)   ' Delete User's Environment
Debug.Print "Delete Duration = " & Timer - lTimer & " s" ', "Count = " & .Count
Debug.Print "- " & (GetTickCount - t) / 1000 & "s"
Debug.Print "Environment(""" & sEnvType & """).Count = " & .Count
End With
End Sub



Sub env()
For x = 1 To 37 'для Windows 7
Cells(x, 1).Value = Environ(x)
Next x
End Sub


Option Explicit

#If VBA7 And Win64 Then
Private Declare PtrSafe Function GetTickCount Lib "kernel32" () As Long
Private Declare PtrSafe Function SetEnvironmentVariable Lib "kernel32" Alias "SetEnvironmentVariableA" (ByVal lpName As String, ByVal lpValue As String) As Long
Private Declare PtrSafe Function GetEnvironmentVariable Lib "kernel32" Alias "GetEnvironmentVariableA" (ByVal lpName As String, ByVal lpBuffer As String, ByVal nSize As Long) As Long
#Else
Private Declare Function GetTickCount Lib "kernel32" () As Long
Private Declare Function SetEnvironmentVariable Lib "kernel32" Alias "SetEnvironmentVariableA" (ByVal lpName As String, ByVal lpValue As String) As Long
Private Declare Function GetEnvironmentVariable Lib "kernel32" Alias "GetEnvironmentVariableA" (ByVal lpName As String, ByVal lpBuffer As String, ByVal nSize As Long) As Long
#End If

Sub test_ENVIROMENT_READ_WRITE2()
Dim t As Long
t = GetTickCount
SetEnvironmentVariable "NLS1_LANG", "test: AMERICAN_AMERICA.CL8MSWIN1251" 'установка переменной
Debug.Print GetEnvironmentVar("NLS1_LANG") ' чтение переменной
Debug.Print "= " & (GetTickCount - t) / 1000 & "s"
t = GetTickCount
SetEnvironmentVariable "NLS1_LANG", "test: =========" 'установка переменной
Debug.Print GetEnvironmentVar("NLS1_LANG") ' чтение переменной
Debug.Print "= " & (GetTickCount - t) / 1000 & "s"
t = GetTickCount
SetEnvironmentVariable "test", "test: 111111111" 'установка переменной
Debug.Print GetEnvironmentVar("test") ' чтение переменной
Debug.Print "= " & (GetTickCount - t) / 1000 & "s"
t = GetTickCount
SetEnvironmentVariable "test", "test: ************" 'установка переменной
Debug.Print GetEnvironmentVar("test") ' чтение переменной
Debug.Print "= " & (GetTickCount - t) / 1000 & "s"
End Sub

'===

Function GetEnvironmentVar(sName As String) As String
    GetEnvironmentVar = String(255, 0)
    GetEnvironmentVariable sName, GetEnvironmentVar, Len(GetEnvironmentVar)
    If InStr(1, GetEnvironmentVar, Chr$(0)) > 0 Then GetEnvironmentVar = Left$(GetEnvironmentVar, InStr(1, GetEnvironmentVar, Chr$(0)) - 1)
    GetEnvironmentVar = sName + ": " + GetEnvironmentVar
End Function



SetEnvironmentVariable "test", Empty 'удаление переменной

Success := SetEnvironmentVariable(PChar(VarName), nil)