You want to call GetText of TCountdownDialog_Frm? You cannot because you declared it as "private". "Private" means: Only the class to which this method belongs can call it (and all other classes which are in the same unit - but this is not so good because it breaks encapsulation). But you can move it to the public section, or, better since you also have a SetText, you can declare a public property Text with GetText as "getter function" and SetText as "setter function:
type
TCountdown_Frm = class(TForm)
...
private
function GetText: String;
procedure SetText(const Value: String); // you have "Integer" here, I suppose you mean "String"
...
public
property Text: String read GetText write SetText;
end;
Remark: the variable Str which is accessed by GetText/SetText is declared outside the class as a global variable. This is against OOP principles because when you instantiate a second form of TCountDown_Frm both forms are fighting for the same data variable, probably not what you want. If you move Str into the scope of TCountDown_Frm you can even drop the getter and setter functions:
type
TCountDown_Frm = class(TForm)
private
Str: String;
...
public
property Text: String read Str write Str;
end;
[EDIT] Handoko was faster...