Do any of you design folks know of a way to select a dimension such as 250.5 in Photoshop instead of 250 or 251?

I keep getting told i need to use the next full value for a crop im making and its kinda taking 3 times as long to do what i want because im having to crop the pics manually

Anyone know of a plugin or anything that will let me select half pixels in PS?

Regards,

Lee