UpLowerCase

Public Declare Function CharUpper Lib "user32" Alias "CharUpperA" (ByVal lpsz As String) As String
Public Declare Function CharLower Lib "user32" Alias "CharLowerA" (ByVal lpsz As String) As String

Private Sub Command1_Click()
Text1 = CharUpper(Text1)
End Sub

Private Sub Command2_Click()
Text1 = CharLower(Text1)
End Sub

Assumes:
1 x textbox
2xcommand buttons(command1:upper,command2:lower)