Hi there,
FileMaker's checkbox fields don't scroll, unfortunately. You might think about showing the same field several times (possibly on different tabs within the resources tab), each with its own value list containing a different subset of your resources. So you may want to keep the Resources value list with all 80 resources, but create 3 or 4 other value lists each with some segment of your resources and show those to users. This is especially nice if your resources naturally come in a few different types.
You can even get creative and put new buttons on these partial lists that say "select all". Clicking this would check or uncheck all of a subset of resources.
For example, if you has a value list named "Dump Trucks" (and other value lists with other truck types) you could set the filter field to
ValueListItems ( get ( FileName ) ; "Dump Trucks" )
to select all of them. To remove all of them you'll need a custom function like
Zap Values which removes the contents of list a from list b. List A in this case would be
ValueListItems ( get ( FileName ) ; "Dump Trucks" )
were "list b" would be your filter field, which may have other resources selected in it besides your subset of dump trucks. Hope that helps.
John