[gradsusr] a problem

[san luo]

Dear group ;
           I have a question ,the words below is a .gs file.it doesn't
work.I think the problem may be the function vint. who can help me ??
'sdfopen d:\vwnd.mon.mean.nc'
'set t 1 '
'set lev 1000 100'
'set lat -90 90'
'set lon 0 360'
'define a=ave(vwnd,lon=0,lon=360)'
'set t 1 '
'set lev 1000 100 '
'set lat -90 90'
'set lon 0 360'
*'define p=lev'
'define f=((-vint(lev,a,100)*6.28*100)/9.8*6370000*cos(lat))/10000000000'
'set gxout contour'
'd f '