Option Explicit

' Create a command button and three text boxes
'  to run the following code

Private Sub Command1_Click()

    Dim inputOK As Boolean
    
    Call checkInputs(inputOK)
    
    If inputOK Then
        MsgBox "continue"
    Else
        MsgBox "oops"
    End If
    
End Sub

Private Sub checkInputs(ByRef okInput As Boolean)

    Dim a As Integer
    Dim b As Integer
    Dim c As Integer
    
    a = Val(Text1)
    b = Val(Text2)
    c = Val(Text3)
    
    okInput = False

    If a <= 0 Then
        MsgBox "bad a input"
    ElseIf b <= 0 Then
        MsgBox "bad b input"
    ElseIf c <= 0 Then
        MsgBox "bad c input"
    Else
        okInput = True
    End If

End Sub