Arithmetic blocks? One that multiplies by 1000 and the other that adds ?
Or is the range of values not set in advance? Is the range variable? For example if one time a = 123 b = 456 then you want 123456 as output; if the next time a = 123 and b = 45 then would you want 12345 as output, or would you want 123045 as output?
What result do you want if one of the values is negative? If both of them are negative then do you need a negative result?