Question about Run-time error '91'

I am receiving the Run-time error '91': Object variable or With block variable not set
at the line of code Sheets("FOR COPY MACRO").Range("W1").Value = ie.document.all.Item("txtTotalCommitIB").Value
in which I am assigning one of the cells in my workbook the value in a text field on a web page.
However, when I go into the code to debug it, the program runs correctly when I hit the continue button. Any ideas why it might be working, but not working at the same time?

Hi,

maybe item is not found …

Probably better to post more of the code.