🚀 go-pugleaf

What program are you using? This is not default Windows behavior. It sounds like the program you are using makes use of something called "dead keys". These are built into the Mac, but not Windows systems (although it sounds like a program you have users them). Basically, when one key is pressed, the computer waits for a second key. If the combination works correctly, then a special character is created. If not, the two characters are output separately.  

This works extremely well for typing foreign languages where accents abound. However, there is nothing you can do to get a character out that is not programmed in. The character you want may be created with alt-0252 (you must use the keypad ... it won't work with the numbers above the letters). This is u with two dots. (umlaut). If you really want u with two acute accent marks, you will need a Unicode font, and some way to get the character.  

There is a utility in Windows Start/Programs/Accessories/Character Map. You might be able to cut and paste from it. Do a test to make sure that the character appears on all the printing you plan to do before spending hours inputting it.