vim - Run ex command to go to line from function in normal mode

Question

I have a function setup to run on InsertEnter autocmd. In the function I want to jump to a specific line.

So what I have tried (simplified) is this so far:

function JumpToLineBeforeScroll()
    echom "function runs"
    exe ":10"
    return ""
endfunction

autocmd InsertEnter * call JumpToLineBeforeScroll() | set cul

I verified using mode() that while this function runs it is in normal mode (pls correct me if wrong). Function runs but the line jump is not working. How do I get this to work ?

Note: What I am actually trying to achieve is on mouse scroll while in insert mode, switch to normal mode, save the current line number and then scroll. Then once I press i to enter insert mode again (InsertEnter) I want to jump back to the last line I was on before scroll. As this would need some conditionals I want to keep this in a function instead of writing the entire code in the autocmd line itself.

Thanks!