Moreover, lets for example the fnControlName=D1_3. How can i refer to its value (D1_3) in order to change the textbox height dynamically depence of the name of the field?
There are two parts to the question because the question will be "change the (selected) textbox to a (selected) height."
For the first part, let's say fnControlName will contain or will resolve to the name of the control. Then you can use Me.Controls(fnControlName).whatever-property to touch an arbitrary control where the name is held in a variable.
The second part of the question is, how tall does it need to be? If this is a predetermined height then use
If you were planning to use a dynamically specified value, we would need a little more to be able to offer a solution - like how you intended to select or compute the given height.