VB的 Do...Loop(編號:2090)

position = 1                
   Do While InStr(position + 1, MyText, " ")  
   position = InStr(position + 1, MyText, " ") 
   words = words + 1              
   Loop                    
   Debug.Print words              
                         
    能不能解釋一下第二行是甚麼意思呢?    
                         
    又words的值會隨著空白分隔的數目改變呢?