Open PDF File From Access Form

I have a lot of pdf file that we save every day and name them like this 8012012,8022012, that are 2 digits day, 2 digits month and four digits of years no slashes. The fields are txt fields that we receive from banks. After processing their data, the upper management wants me to open those pdf files form access . I have created form named frmOpenPdf, placed text box named txtName and placed also command button named cmdOpen . I research code over internet and here is below, but it doesn't work;

Dim avCodeFile As CAcroAVDoc
Dim MYSRTING As String
MYSTRING = txtName.Value
Set Acroapp = CreateObject("AcroExch.App")
Acroapp.Show
Set avCodeFile = CreateObject("AcroExch.AVDoc") 'This is the code file
avCodeFile.Open "C:Documents and SettingsDesktopETFPdfFilesMYSTRING.pdf",

I would like to have like this : an user types 08012012 and the code execute to open file names 0802012 in command button .