HI, i need a know what is wrong with this code. If you run then not known, X0, W or XPlace. This code not accept parameter but in tcl yes. This code make a window panned. Thanks Ruben In R: library(tcltk) XPlace<-function(fract){ tkcmd("place",nb1,"relwidth"=fract) tkcmd("place",nb3,"relx"=fract) #tkcmd("place",nb2,"relwidth"=[expr {1.0 - fract}]) tkcmd("place",nb2,"relwidth"=1.0 - fract) } tt<-tktoplevel("background"="black") w<-.Tk.ID(tt) nb1<-paste(w,".left",sep="",collapse=".") nb2<-paste(w,".right",sep="",collapse=".") nb3<-paste(w,".lrhandle",sep="",collapse=".") f1<-tkcmd("frame",nb1,"background"="purple","width"=20) f2<-tkcmd("frame",nb2,"background"="red","width"=20) f3<-tkcmd("frame",nb3,"borderwidth"=2,"relief"="raised","background"="orange","cursor"="sb_v_double_arrow") tkcmd("place",nb1,"relheight"=1,"anchor"="nw") tkcmd("place",nb3,"rely"=.9,"anchor"="e","width"=10,"height"=10) tkcmd("place",nb2,"relheight"=1,"relx"=1,"anchor"="ne") tkcmd("bind",nb3,"<Configure>","set W [winfo width .]") tkcmd("bind",nb3,"<Configure>","set X0 [winfo rootx .]") tkcmd("bind",nb3,"<B1-Motion>","XPlace [expr {(\"%X\"- $X0)/double($W)}]") XPlace(.5) In Tcl/Tk: proc XPlace {fract} { place .left -relwidth $fract place .lrhandle -relx $fract place .right -relwidth [expr {1.0 - $fract}] } frame .left -bg purple -width 20 frame .right -bg red -width 20 frame .lrhandle -borderwidth 2 -relief raised -bg orange -cursor sb_v_double_arrow . configure -bg black place .left -relheight 1 -anchor nw place .lrhandle -rely .9 -anchor e -width 10 -height 10 place .right -relheight 1 -relx 1 -anchor ne bind .lrhandle <Configure> {set W [winfo width .]; set X0 [winfo rootx .]} bind .lrhandle <B1-Motion> {XPlace [expr {(%X-$X0)/double($W)}]} XPlace .5 pack [ label .left.label -text "Left side" ] pack [ label .right.label -text "Right side" ] Why i can pass parameter in Tcl but with function in R not.?