You can use the build function in the query builder to get what you are looking for.
For first names it goes like...
FName: Left([tblStudent]![stuName],(InStr([tblStudent]![stuName]," ")-1))
Here you find the space in the name field (InStr([tblStudent]![stuName]," ") and then use it as the number in the Left function. You end up retrieving everything to the left of the space.
For last names it is tricky, it is like...
LName: Right([tblStudent]![stuName],(Len([tblStudent]![stuName]))-(InStr([tblStudent]![stuName]," ")))
Here it is similliar, but you have to establish the length of the field forst (#of char) with this function
(Len([tblStudent]![stuName])
Then you SUBTRACT the number representing the locaiton of the space
-(InStr([tblStudent]![stuName]," ")
These two combined reveal the # of char it is that the last name occupies. Now you can use the RIGHT function to extract the exact # of char of the last name for the field. The RIGHT function starts at the right and goes towards the left the # of char you tell it to.
The above example is based off of a table called tblStudent which has both the first and last name of a person in a single field called stuName.
I hope this helps