How to check for dll if exist

[senatin]

how to see if dll is already running or being used?
i want to 
 

$timelap = timerinit()

while 1
    if Exists("dllsample.dll") then
        dllclose("dllsample.dll")
    elseif Exists("dllsample.dll") And Timedeff($timelap) >= 5000 Then
        ConsoleWrite("error. dll problem")
        exit
    else
        exitloop
    endif
Wend

Local $handle = dllopen("dllsample.dll")
.....

I found this  _WinAPI_LoadLibrary() and _WinAPI_GetProcAddress(), are they the one I needed?
I dont fully understand what are they for. Please someone help me

Edited September 29, 2017 by senatin