Put a method in unit 2 that accepts your ttabsheet control as a parameter. Since tab sheet is a common control you should be able to gain access to the control that way..
Unit 2
Procedure ShowHelp(theTabCOntrol:TTabControl,.....);
You will need also the use the Unit in the users list for that control type, too..
etc..
I think you get the idea..
It seems that such variable is ot seen, did you have declared it in the interface or implementation section ?