If use this method for an event and put the code below from the SubRoutine in the DialogCallback Case statement, uncommenting the first line, all my rows disappear from the grid except for the first line when I click on the column header to sort:

DialogObject(TGR_Handle,co_TGR_grid,dlgobject_addevent,"HeadClick",g_HeadClick)

If use this method for an event then it works as expected:

ObjectEventAdd(grid,"HeadClick","Get_HeadClick")

#DefineSubRoutine Get_HeadClick(col_num)

; col_num = DEInfo.Parameters(1).Value
gname = grid.Columns(col_num).DataField
gtext = grid.Columns(col_num).Text
Message(DEInfo,StrCat("g_HeadClick",@CRLF,col_num,@CRLF,grid.Columns.Count,@CRLF,gname,@CRLF,gtext))
If IsDefined(%gname%_sort_ord) Then
If %gname%_sort_ord == "ASC" Then
%gname%_sort_ord = "DESC"
myREC.Sort = "%gname% DESC"
Else
%gname%_sort_ord = "ASC"
myREC.Sort = "%gname% ASC"
EndIf
Else
myREC.Sort = "%gname% ASC"
%gname%_sort_ord = "ASC"
EndIf

#EndSubRoutine

The whole sort question aside I was curious why the exact same code produces different results depending on the approach taken.

Here is a code snippet of the COM EVENT:

Case msg_comevent ; ComEvent
Switch(DEInfo.Identifier)
Case g_HeadClick
col_num = DEInfo.Parameters(1).Value
gname = grid.Columns(col_num).DataField
gtext = grid.Columns(col_num).Text
Message(DEInfo,StrCat("g_HeadClick",@CRLF,col_num,@CRLF,grid.Columns.Count,@CRLF,gname,@CRLF,gtext))
If IsDefined(%gname%_sort_ord) Then
If %gname%_sort_ord == "ASC" Then
%gname%_sort_ord = "DESC"
myREC.Sort = "%gname% DESC"
Else
%gname%_sort_ord = "ASC"
myREC.Sort = "%gname% ASC"
EndIf
Else
myREC.Sort = "%gname% ASC"
%gname%_sort_ord = "ASC"
EndIf
Break