Hi Hit !!
To make a Yes/no msgbox, I will use my Basic knowledge to explain it to you
code:
Val=Interop.Call("User32.dll", "MessageBoxW", WndHandle,'Message','Title', Param);
// WndHandle can set to 0 if MsgBox is not attached to a window
// Param :
// 4 = MB_YESNO
//
// 16 = MB_ICONERROR
// 48 = MB_ICONEXCLAMATION
// 32 = MB_ICONQUESTION
// 64 = MB_ICONINFORMATION
//
// So, if you want a Yes/No MsgBox with an error icon, Param=4|16
//
// If Yes button pressed : Val=6
// If No button pressed : Val=7