Hi Chaim

>Some one can give me information about this function and when do I have to use with this?

EVAL() is used to evaluate an expression and return the result. This is often used to resolve a reference to an object when one of several could be used. Code like this:

DO CASE
  CASE lcName = 'FirstObj'
    loRef = This.FirstObj
  CASE lcName = 'NextObj'
    loRef = This.NextObj
  CASE lcName = 'OtherObj'
    loRef = This.OtherObj
ENDCASE

can be replaced by simply:

loRef = EVAL( "This." + lcName )

which avoids the necessity of hard-coding all the alternatives and is much more efficient too.