I am not sure what you mean by a textboxmailmergefield.

Don't use textboxes.  They don't work very well with mailmerge.

Instead, create a custom lable mailmerge maindocument that contains an 8
cell table the dimensions of the cells of which are as you require them,
and insert a <<Next Record>> field in cells 2 through 8.

Alternatively, use a Catalog (or in XP and later, Directoy) type mailmerge
document in which you set up the mergefields in a one row table in the main
document.  Size that row so 8 of them will fit on a sheet and then execute
the merge.  In that case, you only need set up the ticket once and you do
not need any <<Next Record>> fields.