Insert Pic Into Comment For Every Cell That Has Text Containing String .jpg Or .png

I need a nudge in the right direction with how to amend the below code so that it :
1: cycles though all cells in a workbook, and sees whether the text reference of the cell contains a picture filename (i.e. searches for .png or .jpg in the cell contents)
3: if (1) is correct, it retrieves the picture from "C:/Users/jeff/Documents/Standards/" and pastes it as a cell comment background in the cell to the right (and overwrites any comment backgrounds that might already exist there)

The code below does something a bit different: it looks in a defined range, then adds a comment with a background picture retrieved based on the text in the cell to the left.

I'm sure this is a pretty basic change, but my VBA skills aren't up to it...I've only just started reading though Walkenbach's Power Programming! I'm using Excel 2007

Sub InsertComment()
'www.contextures.comxlcomments03.html
Dim rngList As Range
Dim c As Range
Dim cmt As Comment
Dim strPic As String

On Error Resume Next

Set rngList = Range("A1:A5")
strPic = "C:/Users/jeff/Documents/Standards/"
On Error Resume Next
For Each c In rngList
With c.Offset(0, 1)...................