BCGControlBar Pro for MFC
void CBCGPEdit::EnablePopupDialog ( CRuntimeClass *  pRTI,
LPCTSTR  lpszTemplateName,
BOOL  bIsResizable = FALSE,
BOOL  bComboBoxMode = FALSE,
BOOL  bIsRightAligned = FALSE 

Enables drop button and puts the edit control in "popup dialog" mode.

pRTIThe popup dialog runtime class. Should be derived from CBCGPDialog
lpszTemplateNameThe popup dialog resource name.
bIsResizableSpecifies whether the popup dialog is resizable or not.
bComboBoxModeIf this parameter is TRUE, the control behaves like a combo box in drop list mode (there is no caret and edit cusror and user cannot select text inside the edit box).
bIsRightAlignedSpecifies whether the popup dialog is right-aligned or not.