Setcapture does not seem to succeed in the window

Below CodeIf you do not use picture for implementation, but directly use form for implementation, it seems that it is not very successful.
Private sub picture1_mousemove (button as integer, shift as integer, X as single, y as Single)
Dim bmousein as Boolean
Bmousein = (0 <= x) and (x <= picture1.width) and (0 <= Y) and (Y <= picture1.height)
Debug. Print X, Y, bmousein
If bmousein then
Setcapture picture1.hwnd
If lstate = 0 then
Lstate = 1
Me. Height = 2400
Else
End if
Else
Releasecapture
If lstate = 1 then
Lstate = 0
Me. Height = 120
Else
End if
End if
End sub