You need to provide a unique pointer to each of the elements in each of the Tab Boxes. Below is one way to do that
counter = 0;
Chart_func = function( {Layer},
counter++;
eval(Substitute(
Expr(
V List Box(
Outline Box( Layer ),
H List Box( Text Box( "enter NEW CL: " ), __theBinNumber__ = Number Edit Box() ),
Button Box( "OK", __NEW_CL__ = __theBinNumber__ << get )
)
),
Expr( __theBinNumber__ ), Parse( "theBinNumber" || Char( counter ) ),
Expr( __NEW_CL__ ), Parse( "NEW_CL" || Char( counter ) )
))
);
MTK72Mon_TAB = Tab Box(
" TIN_LD ", Chart_func("TIN_LD"),
" TIN_HD ", Chart_func("TIN_HD"),
" CU 225A ", Chart_func("CU_225A"),
);
MTK72_Mon_charts = new window ("MTK72 Mon",hlistbox("Title"), MTK72Mon_TAB);
Jim