DevExpress dxBar controls use

In the menu manager added dxBarButton
DxBarButton Visible into ivalway, not TRUE, how to do ah,
I am in the main window dxBarButton. Visible:=ivalways; Yes,
But in the other window call mainForm. After the main window mainForm dxBarButton. Visible:=ivalways; Is an error, ivalways show red wavy lines,

Warrior, please help, thank you,