How exactly you would do that would depend on the environment your code is running in: The first bit is easy:
string k = "labelA1";
Hashtable[k] = ...
It's the second bit that changes.
For web based, then this might do it:
string = "labelA1";
Control c = FindControl(k);
Label l = c as Label;
if (l != null)
{
Hashtable[k]=l.Text;
}
If it isn't, then we need to know what you are running in...