understanding a code

[brodaddy2002]

I found this code on the internet, but cannot find it again. My question is, what does the numbers 8 and 0 mean? What do they do? Does KeyAscii = 0 make the value "null"?

Private Sub StrikeAltText_KeyPress(ByVal KeyAscii As MSForms.ReturnInteger)
‘StrikeAltText is the name of the textbox that the user is entering data

Select Case KeyAscii
Case vbKey0 To vbKey9, 8 ‘ I don’t have any idea what the number 8 does.
Case Else
KeyAscii = 0
Beep
End Select

End Sub

Any Help will be greatly appreciated.

 

[Colin Legg]

The 8 is the equivalent of the back key. It would be clearer to use vbKeyBack instead of 8.

Yes, the 0 is equivalent of null. Have a look at an ASCII table, eg:
Ascii Table - ASCII character codes and html, octal, hex and decimal chart conversion

 

[brodaddy2002]

I guess another easy softball. What does the comma(,) mean in the program? The select case chooses the numeric values 0 through 9, and then executes a backspace? I completely understand the case else on. I am just not sure about the Case vbKey0 to vbKey9, 8 line.

 

[Fazza]

please refer http://msdn.microsoft.com/en-us/library/vstudio/cy37t14y(v=vs.100).aspx

the comma separates the possibilities

 

[brodaddy2002]

Copy All. It is starting to become clear. One more quick question. In the top line, we use ByVal KeyAscii As MSForms.ReturnInteger. Do we have to use MSForms.ReturnInteger? Can we simply just say ByVal KeyAscii As Integer?

 

[Colin Legg]

The piece of code is an event handler. It has a special signature and if you change it then the code won't work - in fact, it's very likely the code won't even compile. If you really wanted to, you could probably get away with removing the MSForms qualifier, leaving you with:
Private Sub StrikeAltText_KeyPress(ByVal KeyAscii As ReturnInteger)

but it's bad practice to do so. ReturnInteger is not the same as Integer: ReturnInteger is actually a class in the MSForms library. It's best just to leave the MSForms. qualifier in there in case you have a reference to another library which also has a class called ReturnInteger (which would cause a clash). Perhaps it will make the fact that MSForms.ReturnInteger is an object (an "object" is an instance of a class) if we use its Value property explicitly?

Private Sub StrikeAltText_KeyPress(ByVal KeyAscii As MSForms.ReturnInteger)
    'StrikeAltText is the name of the textbox that the user is entering data
 
    Select Case KeyAscii.Value
        Case vbKey0 To vbKey9, vbKeyBack
            'OK
        Case Else
            KeyAscii.Value = 0
            Beep
    End Select
 
End Sub

 

[brodaddy2002]

You guys truly are the zen masters of excel. Thank you very much.