How ?

[Arsilex]

        gridMaps = guiCreateGridList(639,99,356,511,false) 
        guiGridListSetSortingEnabled(gridMaps,false) 
        guiGridListAddColumn(gridMaps,"Map name",0.9) 
        guiSetAlpha(gridMaps,0.69999998807907) 

how to put in this all maps of Race?

[DiSaMe]

getResources 
getResourceInfo 
triggerClientEvent 
addEvent 
addEventHandler 
guiGridListAddRow 
guiGridListSetItemText 

Get all resources with getResources, cycle through all of them and use getResourceInfo to check if "type" attribute is "map" and "gamemodes" attribute is "race", and if they are, then also get "name" attribute and put it into a table. So you have a table with the names of all race maps. Make an event client-side and trigger it from server with map names list as an argument. On the client side, loop through that table and use guiGridListAddRow and guiGridListSetItemText to add the map names to the grid list.