IAC : C# : Is it possible to get bounding box of a field as an AcroRect object ?

Is it possible to get bounding box of a field as an AcroRect object ?

CAcroApp acroApp = new AcroAppClass();  
CAcroAVDoc avDoc = new AcroAVDocClass();
CAcroRect acroRect = new AcroRectClass();
CAcroPDDoc pDDoc = new AcroPDDocClass();

if (!avDoc.Open(sample_pdf, ""))
  return;
else
  pDDoc = (CAcroPDDoc)avDoc.GetPDDoc();

IAFormApp formApp = new AFormAppClass();
IFields myFields = (IFields)formApp.Fields;
IEnumerator myEnumerator = myFields.GetEnumerator();

while (myEnumerator.MoveNext())
{
  IField myField = (IField)myEnumerator.Current;
  string fieldName = myField.Name;
  string fieldType = myField.Type;
}

I need to replace  myField of  type checkbox to a text field of same size at same location. I can remove checkbox by 

while (myEnumerator.MoveNext())
{
  IField myField = (IField)myEnumerator.Current;
  string fieldName = myField.Name;
  string fieldType = myField.Type;
  //Remove Checkbox field type
  if(fieldType=="checkbox")
     myFields.Remove(fieldName);
}

How can I add a text type field in the same position of checkbox ?

 
if(fieldType=="checkbox")
{
//Remove Checkbox field type
  myFields.Remove(fieldName);
//Add text field type
  myFields.Add(fieldName, "text", 0, acroRect.Left, acroRect.Top, acroRect.right, acroRect.bottom); // how to get acroRect object of a field ??
}