I have problem here. I used common dialog, how I open A.tin and A.dat in one time?

Code:
dlgOpen.Filter = "(*.tin)|*.tin|"
dlgOpen.ShowOpen
InputFileTIN = dlgOpen.FileName
dlgOpen.Filter = "DAT File (*.dat)|*.dat|All File |*.*"
dlgOpen.ShowOpen
InputFilePoint = dlgOpen.FileName 
txtPoint = dlgOpen.FileName