convert negative value in textbox to positive value on userform

I search for way to solve this problem . what I want after select name from combobox2 if the value in textbox2 less than value in textbox4, then the value in textbox5 should be positive . I using many way like function Abc or *-1 but doesn't work .
also posted here
https://www.mrexcel.com/board/thread.../#post-5967704
I hope finding help .