Simple math in conditionals

[bpacilio]

Ok,
This should be easy but I can not find it in the help. I'm setting up conditions for when the user hits the next button in a dialog. I want to launch a dialog if the difference between two numbers (properties) in not 0. It seems that you can only do >,<,= kind of comparisons but not something like
PROP1 <> 0 And ((PROP2 - PROP3) <> 0)
The properties are all numbers but this fails.

[RobertDickau]

No, MSI condition syntax doesn't support arithmetic; instead of testing if the difference is nonzero, can you test if the two property values exist and are unequal?

[bpacilio]

I need a value of 0 to do the install. I figured I could not do it in the conditionals so I stated an InstallScript. I have the following but it does not work. Either I missed something or I have it in th wrong place in the sequence. According to the help I have to put it in the exec sequence. I have it after CostFinalize but I don't see my variables change and I don't get the MessageBox. Any Ideas?

function SetUpdateValue(hMSI)
	NUMBER nvSize,nvCurr,nvNew,nvDiff;
	STRING svNewVersion,svCurrentVersion,svUpdateVal;
begin
	nvSize=20;
    MsiGetProperty (hMSI, "NEW_VERSION",svNewVersion , nvSize);
    MsiGetProperty (hMSI, "IS_STARS_UPDATE", svCurrentVersion, nvSize); 
    StrToNum(nvCurr,svCurrentVersion);
    StrToNum(nvNew,svNewVersion);
    nvNew = nvNew-nvCurr; 
    MessageBox("In InstallScript",INFORMATION);
    NumToStr(svUpdateVal,nvNew);
	MsiSetProperty(hMSI, "UpdateConditionVal", svUpdateVal);
end;

[RobertDickau]

You'll generally want to reset the buffer-size variable (nvSize) before each call to MsiGetProperty.

If you display the results of MsiGetProperty, are the values what you expect?

[bpacilio]

I can't seem to verify that the custom action is getting run let alone the values of the Set And Get. I try to use the MSI debugger but it starts to run the program before I can set break points. I don't see my custom action though. Can anyone suggest the best place in the Exec Sequence to place it?

[RobertDickau]

It depends on how you're using the results, but for testing that it's running at all, anywhere in the Execute sequence should be fine.

[bpacilio]

I don't know why this works. I move the action from the execute sequence to the UI sequence and it works. I get the information I need. It's odd because I saw some notes that say that the get and set should be run in the exec sequence.