User Entered Value to Change/Affect Measure

Hello All,

This is a shot in the dark and I dont think it is possible but I wanted to check if anyone knew of a way to accomplish this. I need to use a text box, that a user can enter a value, say 500, and after entering it, it affects a measure. So in my instance its a QuantityOnHand measure. I want them to be able to type a number into the text box, and the measure would add/subract that number to the Quantity

QuantityOnHand = [QuanOnHand] + [UserTypedValue]

I have this functioning with a table I made and a slicer, which the slicer then affects the measure like so:

QuantityOnHand = [QuanOnHand] + SELECTEDVALUE(Data[UserTypedValue])

However this is not ideal. My number could be anywhere from -2000 to 2000. I have a table with sequential numbers laid out to be selected from by the slicer but whenever you search for a number like '12' for example. You get 1201, -1201, 120, -120, etc and it becomes really difficult to find the number that you actually want to use.

Any help would be appreciated