現在はプラグインの数だけ並べていきなり↓なことをしてます
Public Declare Function GetJpg Lib "IfJpeg.spi" Alias "GetPicture" (…) As Integer
Public Declare Function GetBmp Lib "IfBmp.spi" Alias "GetPicture" (…) As Integer
…
Do
If Exist("IfJpeg.spi") Then rtn = GetJpg(…)
If rtn = 0 Then Exit Do
If Exist("IfBmp.spi") Then rtn = GetBmp(…)
If rtn = 0 Then Exit Do
……
Loop While False