Windows only support three buttons and the mousewheel by default.
Windows 2000 & XP however also supports something called X buttons.
So pressing a 4:th mousebutton should generate a WM_XBUTTON message, just like pressing a "browserkey" on a keyboard would generate a WM_APPCOMMAND message.
But I don't know if Blitz handle those messages.
Read more here...
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/userinput/mouseinput/aboutmouseinput.asp
[Edit]
If Blitz gets mouseinput from DirectX using the DIMOUSESTATE structure I think it only allows button 0-3.
I know DX8 & DX9 has an additional structure called DIMOUSESTATE2 which supports up to 8 buttons, but if DX7 has it or not, I don't know.
Windows 2000 & XP however also supports something called X buttons.
So pressing a 4:th mousebutton should generate a WM_XBUTTON message, just like pressing a "browserkey" on a keyboard would generate a WM_APPCOMMAND message.
But I don't know if Blitz handle those messages.
Read more here...
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/userinput/mouseinput/aboutmouseinput.asp
[Edit]
If Blitz gets mouseinput from DirectX using the DIMOUSESTATE structure I think it only allows button 0-3.
I know DX8 & DX9 has an additional structure called DIMOUSESTATE2 which supports up to 8 buttons, but if DX7 has it or not, I don't know.