library(tcltk)
dat = read.table("GRB.dat",head=T)
doit = function(...) {
  val = as.numeric(tclvalue(tv))
  hist(dat[,2],prob=T)
  lines(x,dexp(x,val),col="red")
}
x = seq(0,140,0.1)
tt = tktoplevel()
tv = tclVar(0.01)
scl = tkscale(tt, comm=doit, from=0.01, to=0.04, reso=0.005,
orient="horizontal", variable=tv)
lab = tklabel(tt,text="lambda")
butt = tkbutton(tt,text="Close", comm=function() tkdestroy(tt))
tkpack(lab,scl,butt)