VBA and Function Pointers

sjreryan · November 18, 2023, 11:57pm

For those with Clarion 11 and its new function pointer support this article might be of interest if you are working with MS Office VBA and want to do fancy things like send back row and column values via a function pointer. Although you might just clipboard the contents or XML them…

Loop through excel sheets seems a bit slow using late binding. In Csharp you get grab whole sheets as a object range.

But if your using clarion and dont want to call dot net this might be something worth exploring…

gist.github.com

https://gist.github.com/sancarn/940556cc1ff7806ca0e742a0c4117ab3

How to use a function pointer in VBA.md

VB6 and VBA come with no support for function pointers.

Also, when you wish to execute a function in a dll using the Declare function, you can only call functions created by the Steadcall calling conversation.

These constraints can be avoided by using the DispCallFunc API.
The DispCallFunc is widely used in VB6 when erasing the history of IE.
Although the DispCallFunc is known as API for calling the IUnknown interface, in fact, you can also perform other functions other than COM by passing the NULL to the first argument.

As explained in the http://msdn.microsoft.com/en-us/library/ms221473(v=vs.85).aspx , the DispCallFunc argument is as follows.

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CarlBarnes · November 20, 2023, 3:50pm

There’s 3 or 4 pages of code and text. Can you extract some of the interesting code and paste it here, plus show some possible Clarion code?

sjreryan · November 20, 2023, 9:49pm

Of interest to test is this…

lDispCallFuncResult = DispCallFunc(0, AddressOf NoParamNoReturn, _
tagCALLCONV.CC_STDCALL, VbVarType.vbEmpty, _
0, 0, 0, VarPtr(vFuncResult))

This is the address of interest.

AddressOf NoParamNoReturn

Hoping to test this as an address passed from clarion to MS Office VBA and see if we get a call back or its a silly idea…which will result in no call or its a HUNG UP…