Luis,

>SELECT @ing_fon =SUM(mont2)FROM PLPLFMOV AS MOV JOIN PLPLFTAB AS TAB
>ON mov.concep = tab.concep
>WHERE cod_emple = '092754' AND LEFT(MOV.CONCEP,1)='1' AND SUBSTRING(tab.tab_dscto,1,1) = 'F'

If you want to know how to do this against VFP tables, this part:

@ing_fon =SUM(mont2)

should be

SUM(mont2) AS ing_fon

The rest of it should work just fine in VFP.