public extern static Int32 GetThemeBackgroundContentRect(IntPtr hTheme, IntPtr hdc, int iPartId, int iStateId, ref RECT pBoundingRect, out RECT pContentRect);

Declare Function GetThemeBackgroundContentRect Lib "uxtheme.dll" (TODO) As TODO

Public Shared Function GetThemeBackgroundContentRect(hTheme As IntPtr, hdc As IntPtr, iPartId As Integer, iStateId As Integer, ByRef pBoundingRect As RECT, ByRef pContentRect As RECT) As Int32