The FindControl method of the page class can be used to find any control inside a web form, regardless of its location in the page hierarchy. This includes controls that are nested inside other controls, such as controls within a GridView's TemplateField.

To find a control within a GridView's TemplateField, you can use the following steps:

1. Get a reference to the GridView object.
2. Iterate through the rows of the GridView.
3. For each row, find the control within the TemplateField using the FindControl method.

In your code, you are trying to find the HyperLink control with the ID "hlPlus" within the ItemTemplate of the GridView's TemplateField. To do this, you can use the following code:

foreach (GridViewRow row in grvYourOpportunities.Rows)
{
    if (row.RowType == DataControlRowType.DataRow)
    {
        // Get a reference to the HyperLink control.
        HyperLink hlPlus = (HyperLink)row.FindControl("hlPlus");

        // Check if the HyperLink control was found.
        if (hlPlus != null)
        {
            // Do something with the HyperLink control.
        }
    }
}

This code will iterate through the rows of the GridView and find the HyperLink control with the ID "hlPlus" within the ItemTemplate of the TemplateField. If the control is found, it will be assigned to the hlPlus variable. You can then use the hlPlus variable to do whatever you need to do with the control.