You should look at the TableViewSuite sample code as it does this. Basically you set the tag of the label when you create it and you get the subview back like this after you dequeue it:
Code:
// creation
label = [[UILabel alloc] initWithFrame:CGRectMake(0.0f, 12.0f, 70.0f, 25.0f)];
label.tag = LABEL_TAG;
[cell.contentView addSubview:label];
// after dequeue
label = (UILabel *)[cell.contentView viewWithTag:LABEL_TAG];