You can use this code:
private void FindLoop()
{
int intFound = 0;
Word.Document document = this.Application.ActiveDocument;
Word.Range rng = document.Content;
rng.Find.ClearFormatting();
rng.Find.Forward = true;
rng.Find.Text = "I have";
rng.Find.Execute(
ref missing, ref missing, ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing, ref missing, ref missing);
while (rng.Find.Found)
{
intFound++;
rng.Find.Execute(
ref missing, ref missing, ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing, ref missing, ref missing,
ref missing, ref missing, ref missing, ref missing, ref missing);
}
MessageBox.Show("Strings found: " + intFound.ToString());
}