what wrong for my code?

[Al42]

Your code will fail if 2 of the 3 textboxes (or even 1 of them) is blank. Try this.

Private Sub Command1_Click()
Dim degrees As Double
Dim minutes As Double
Dim seconds As Double
Dim decimals As Double

  If Trim$(Text1.Text) = "" Or Trim$(Text2.Text) = "" Or Trim$(Text3.Text) = "" Then
      MsgBox "Please key in your input values", vbInformation, "Degree Converter"
  Else
    degrees = CDbl(Text1.Text)
    minutes = CDbl(Text2.Text) / 60
    seconds = CDbl(Text3.Text) / 3600
    decimals = degrees + minutes + seconds
    Label6.Caption = decimals
  End If

End Sub