I am using a form in BCB, and I want a label to change its caption whenever a variable assigned to it is changed.

The problem is, if I do
void main()
Label1->Caption = variable;
I get an error saying Undefined symbol 'Label1'
how do I define the Label1 in the main?
actually, how do I change the caption whenever the variable change?

is there something like OnExecute, an event that is always happening when the program is running?