Then you mean this...
Do
If Not MyAction(ProLoading_Spr[3]) Then Sync()
Loop
End
Function MyAction( Spr )
Ret = 0
If GetSpriteExists( Spr ) = 1
If GetSpriteScaleX( Spr ) <= 2.7
SetSpriteScaleByOffset( spr, GetSpriteScaleX( Spr ) + 0.0135, GetSpriteScaleY( Spr ) )
Else
Ret=1
EndIf
EndIf
EndFunction Ret
But if it were me, I personally see no point in having two syncs in any game loop? What specifically neds you to sync somewhere else in the code? It makes it very difficult to debug when things go wrong, and I personally think it's bad practice to have multiple screen draws in the code.