com口发ASCII Y,该怎么解决

com口发ASCII Y
各位大师：我现在想实现 如何在串口发送“Y”（ASCII）后，看是否能收到“SM”，如能收到，则没有任何提示，若没有收到“SM”。则提示“通讯错误”
谢谢！

[解决办法]

VB code

Option ExplicitPrivate Sub Command1_Click()    If MSComm1.PortOpen = True Then        MSComm1.Object = "Y"    End IfEnd SubPrivate Sub Form_Load()    MSComm1.Settings = "9600,n,8,1"    MSComm1.PortOpen = True    MSComm1.RThreshold = 1End SubPrivate Sub MSComm1_OnComm()    Select Case MSComm1.CommEvent        Case 2            strsj = strsj & MSComm1.Input            If Mid(strsj, 1, 2) <> "SM" Then                Label1 = "通讯错误"            End If    End SelectEnd Sub