Michel is correct. In a DataView there is no way to send one changed attribute of an object to the server but not another (if both attributes are editable and have been changed, of course).
There are a number of reasons for this, but the primary one is consistency.
Objects are unique and one object is often used in different places at the same time (for example, it exists in a DataGrid and in several different DataViews - all of which are active). The Mendix client therefore has an internal store for objects and when an object is requested (in this case from the UI) it passes back a reference to an existing object if it already contains it.
This allows all views to remain synchronized.
Changes to an object are queued on the client (regardless of which part of the view they originated in) and sent to the server before, for example, a Microflow is invoked.
This ensures that the state of the object that the Microflow is processing on the server is identical to the state of this object on the client.
I'm not a technician, but I suspect it is impossible to commit just an attribute. Objects can be commited, and when they are, so is the value of it's attributes.
What is the case, maybe this can only be solved by commiting the content of the inputfield to a 'parallel object', only used for storing certain values but I don't know if that will do the trick for you