I don't think you can use the SUM function on control names, so try this in the control source of the GRAND box:
Code:
=me!txt_1 + me!txt_2
etc, etc...
if that doesn't work, try replacing "me!" with "reports!mainReportName!txt_1, etc..."
if that doesn't work, try replacing "reports!mainReportName!txt_1 + etc, etc..." with "reports("mainReportName").controls("txt_1") + etc, etc...
if that doesn't work, try summing them in code, on the LOAD event of the form and ending the code with:
Code:
me.Grandtotal = ResultOfCodeArithmetic
HTH!
ps - the second "try this" statement of mine most likely won't work, I just included it because I've never tried it before on a control source. I think that syntax is only meant to work in code.