FC105 SCALE and FC106 UNSCALEfrom the TI-S7 Converting Blocks section in the standard library are probably what you need.
If you're using a S7-400 in combination with S5 analog cards (e.g. over Profibus) you can also use FC100 through FC107 depending on the analog input card you use, and FC108 and FC109 depending on the analog output card. But you can only use these FC's for the S5 analog cards! For the S7 analog cards you still need the former mentioned FC105 and FC106.
You could of course write your own function as well!
Kind regards,
Jean Pierre Vandecandelaere