whenever i used instr() or left() right() mid() etc, i get a "invalid procedure call"

no idea whats going on...

VB Code:
  1. For i = 0 To Len(strSource) Step 1
  2.         If Mid(strSource, i, 1) = Left(strSearch, 1) Then
  3.             For j = 0 To Len(strSearch) Step 1
  4.            
  5.             Debug.Print j + i
  6.             Debug.Print Mid(strSource, j + i, 1)
  7.             Debug.Print Mid(strSearch, j, 1)
  8.            
  9.                 If Mid(strSource, j + i, 1) <> Mid(strSearch, j, 1) Then
  10.                     isitthere = False
  11.                 End If
  12.                
  13.                 If j = Len(strSearch) Then
  14.                     isitthere = True
  15.                 End If
  16.                
  17.             Next j
  18.         End If
  19.     Next i

id use instr() but i keep getting errors with that, and now i get errors with mid() and left()