When creating the custom cell, make sure you are adding the view controller as the button action's target. So in your view controller's (assuming it is the datasource for the table view):
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// All your standard identifier & dequeueing stuff here
if (cell == nil)
{
// We are creating a new cell, let's setup up its button's target & action
cell = [[[CustomCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
[cell.yourButton addTarget:self action:@selector(yourAction:) forControlEvents:UIControlEventTouchUpInside];
}
return cell;
}